Thick-films of Pb₅Ge₃O₁₁ with full density and thickness of 60μm were prepared by rapid-quenching. A pyroelectric detectivity of 10⁷(cm⋅Hz^1/2/W) was obtained, equwalent to that of a commercial infrared detector. Polarization reversal by applied voltage was very slow, indicative of a relaxation phenomenon.

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Crack-free and dense BaTiO₃ films with perovskite structure were obtained at temperature as low as 500°C by the sol-gel process. Barium acetate and tetra-n-butyl orthotitanate were used as raw materials. Glycerol and methanol were used as solvents. The films were deposited on several types of substrates. ICP analysis showed that the Ba/Ti ratio in BaTiO₃ films agreed with that of starting mixtures. Films obtained at 1000°C on a platinum substrate showed a typical P-E hysteresis loop. The spontaneous polarization was 2.3μC⋅cm^-2, the remanent polarization was 0.8μC⋅cm^-2 and the coercive filed was 2.8kV⋅cm^-1. Dielectric constant and dielectric loss angle were about 1000 and 0.035, respectively.

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PbTiO₃ thin films were prepared by activated reactive evaporation (ARE) through controlling evaporation rates of Pb and Ti, O₂ pressure, and substrate temperature. The Pb/Ti ratio of these films depended on the evaporation rate of Ti. When the substrate temperature and O₂ pressure were held at 600°C and 1.6×10^-4 Torr respectively, the optimum evaporation rates of Ti and Pb for a nearly stoichiometric PbTiO₃ film were 0.2 and 1.2-1.8Å/s, respectively. PbTiO₃ films deposited on a c-plane of sapphire showed preferred orientation of (111) plane, and those on (100) plane of MgO showed strong c-axis orientation. AES depth profile mesurements and SEM observations indicated that these films were uniform in composition and dense.

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An uniform and stable iso-propanol solution of mixed alkoxides of lead n-butoxide, zirconium n-butoxide, and titanium n-butoxide was prepared by adding diethanolamine which suppresses the polymerization and hydrolysis of metal alkoxides. PZT thin films were synthesized from this solution by dip-coating technique. PZT thin films having a perovskite structure were obtained on various substrates amd their properties were examined. PZT films formed on the platinum substrate at 700°C showed a ferroelectric hysteresis loop, a remanent polarization of 14μC/cm², and a coercive field of 45kV/cm. Their dielectric constant and dielectric loss angle were 700 and 0.03, respectively.

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The sol-gel method was applied to the preparation of PbTiO₃ fibers. The Pb(CH₃COO)₂⋅3H₂O and Ti(O⋅i-C₃H₇)₄ were brought into reaction in 2-methoxyethanol to form oligomeric Pb-Ti complex alkoxide. The obtained alkoxide was then hydrolyzed in alcoholic solutions by adding a limited amount of water. The gel fibers were drawn from the resulting spinnable sol and converted to tetragonal PbTiO₃ fibers by heating above 500°C. The crystallization behavior of gels and some properties of the resultant fibers were examined.

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Different agglomerated powders of PLZT were prepared from aqueous nitrate solutions using two preparation methods. The microstructure developed during calcination at 450°-470°C was determined by powder characteristics such as crystalline phase, particle morphology and size, agglomeration, and surface area. Green compacts containing 5wt% stearyl alcohol binder were fabricated by uniaxial pressing. Extraction of the binder was carried out with supercritical carbon dioxide at 35°-65°C under the pressure of 9.81MPa or 19.6MPa. The degree of agglomeration of calcined powders influenced the extraction. The extraction process is discussed on the basis of mass-transfer resistance in compacts and chemical affinity between powder surface and stearyl alcohol.

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The authors' research work results, obtained from the Pb(Mg_1/2W_1/2)O₃-Pb(Ni_1/3Nb_2/3)O₃-PbTiO₃ system, are summarized as follows.
(a) The specimens dielectric properties are improved by the columbite precursor method, using MgWO₄ and NiNb₂O₆ as raw materials. The dielectric constant for the specimens sintered at 1000° to 1025°C is above 13000 at 20°C. Its temperature dependence meets the EIA standard specification, Y5U, and the Curie temperature is almost constant with regard to the sintering temperature. The dielectric properties for specimens prepared by the columbite method do not depend on the sintering temperature, unlike those prepared by the conventional method. This feature is advantageous to the dielectric property reproducibility.
(b) Since reactivities for MgO and NiO, supplied by the convenional method, are low, the Pb-W-O compound remains in the sintered specimens and results in decrease in the dielectric constant.
(c) The Curie temperature shift for specimens prepared by the conventional method, with an increase in the sintering temperature, is thought to be caused by the increased fraction of PMW component, which forms from the reaction in the remained Pb-W-O compound with MgO.
(d) DTA characterization data for the powders gave valuable information regarding how to achieve on an effective process control.

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Nb₂O₅ additive effects for sintering and electrical properties were investigated in PZT ceramics using the hydrothermally produced powder. Nb₂O₅ addition in PZT ceramics were suppresive effect for grain growth in sintering properties. On the other hand, Nb₂O₅ addition was contributed to improve the dielectric loss in electrical properties. As the grain size was decreased, the relative permittivity (ε_s) at Curie point (T_c) was decreased, the ε_s curve became suppresive. The values of ε_s at T_c were 80000 (Nb₂O₅=0.005mol) and 40000 (Nb₂O₅=0.01mol), respectively and these exhibited the larger values compared to those made by conventional powder. The electromechanical coupling factors, K_p, were high value above 0.60 at the wide sintering temperature range by Nb₂O₅ addition above 0.005mol.

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Ferroelectric Pb(Fe_2/3W_1/3)O₃ was synthesized by a new two-stage precipitation process. On heating precipitates, PbWO₄, pyrochlore phase, and Pb(Fe_2/3W_1/3)O₃ formed as major reactants at 300°, 510°, and 700°C, respectively. A small amount of a liquid phase that accelerated densification was also found at 680°C. A pure compound of Pb(Fe_2/3W_1/3)O₃ formed at 870°C. However, it melted incongruently at 930°C to form Pb₂WO₅ and facet-shaped magnetic PbFe₁₂O₁₉. The predominant formation mechanism of precipitation-derived Pb(Fe_2/3W_1/3)O₃ is considered to include the formation of pyrochlore phase and its subsequent reaction to form Pb(Fe_2/3W_1/3)O₃. The formation process of Pb(Fe_2/3W_1/3)O₃ in the precipitation method is relatively simple in comparison with the solid-state reaction. This is attributed to the improved homogeneity and reactivity of the starting materials in precipitates.

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The powder synthesis using coprecipitated precursor and dielectric properties of the sintered products have been investigated for Bi₂(Sn_1-xTi_x)₂O₇ solid solutions (0≤x≤0.7). Examination of the coprecipitation procedure showed that rapid mixing of an aqueous nitrate solution (0.1-0.4M) containing required cation species with an excess of aq. NH₃ produced a coprecipitated precursor in which uniform, quantitative deposition of each unlike cation species occurred. The precursor was readily converted to desired solid solutions up to x=0.6 by heating at 500°-600°C, and finally to a highly densified body by sintering at 1000°C. Dielectric constants of various solid solutions were found to increase almost linearly with increasing substitution by Ti⁴⁺, while dielectric anomaly peak temperature indicative of the phase transition from acentric tetragonal to acentric cubic for Bi₂Sn₂O₇ correspondingly decreased. The broadening and shifting of the dielectric anomaly peak with Ti-substitution and/or prolonged sintering were discussed.

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BaTiO₃-based fine powders, with Ba/Ti ratios ranging from 0.98 to 1.05, or comprising CuO up to 1mol%, were synthesized by the spray pyrolysis technique. Starting solutions were prepared by dissolving Ba(NO₃)₂, Ti[(CH₃)₂CHO]₄, and Cu(NO₃)₂⋅3H₂O in diluted nitric acid, and they were sprayed into the reaction chamber at 800°C through a 2-fluid atomizer with pressurized oxygen gas. The obtained powder particles were hollow spheres 2μm across on the average, which consisted of very small primary particles of around 10nm. The powders were mostly BaTiO₃ with small amounts of residual compounds, which however, were removed completely by calcining at 620°C for 1h in an oxygen atmosphere. The calcination at 620°C did not change the particle size. The Ba/Ti ratio of the powders affected the density and the microstructure of sintered bodies. An excess of BaO enhanced densification and gave a grain size discernibly larger than that of stoichiometric composition, whereas a sample containing excess TiO₂ component showed marked grain growth which caused the lower bulk density. When the Ba/Ti ratio was 1.03, the relative densitiy of 95% was achieved at the lowest sintering temperature of 1250°C without sintering aids. It should be noted that addition of CuO to the powders with Ba/Ti ratio of 1.03 contributed to reducing the sintering temperature. Addition of 0.5mol% CuO decreased the sintering temperature to 1060°C. The obtained sintered body showed a dielectric constant of 2300, dielectric loss of 0.9% at room temperature, and Curie temperature of around 130°C.

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Diopside ceramics were fabricated by firing glass compacts with the composition of MgO-CaO-2SiO₂ at various temperatures for 1 hour and the applicability of these ceramics to low loss dielectrics was investigated. A sharp shrinkage of diopside glass compacts was observed in a few minutes at 800°C by the viscous flow mechanism and then the transformation into diopside ceramics by precipitation of diopside crystals proceeded at 858°C. Diopside ceramics were obtained by firing in the temperature range from 900° to 1200°C. The bending strength of sintered bodies obtained at 900°C was about 200MPa and decreased with increasing firing temperature. The linear thermal expansion coefficient of diopside ceramics was 10×10^-6°C^-1, and the dielectric constant and loss tangent were 7.1 and 2×10^-4, respectively.

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The relation between the drying condition of precipitated gels and the transparency of PLZT ceramics was studied. The drying condition affected the transparency of ceramics. The highest transparency was obtained when the precipitated gel was dried by the solvent-exchange technique using acetone. The transparency decreased when the calcined powder had a cohesive nature. In order to prepare an aggregate-free powder after calcination, it was necessary that the precipitated gel was coagulated in the organic solvent used in the drying procedure. If the gel was intensionally coagulated in aqueous solution of ammonium carbonate, the dried powder was non-aggregated, and transparent ceramics was made without using an organic solvent. The coagulated structure of gel in a solvent was retained after drying and calcination, so that a powder with a small amount of internal pores was obtained by grinding, because of its weak cohesive strength.

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To clarify the sintering process of glass/alumina composites, we examined the microstructure of glass/alumina composites fired at various temperatures using SEM (Scanning Electron Microscope). The formation of pores in glass/alumina composites was studied by observing the softening and foaming phenomena of glass. The softening and fluidity of glass above 700°C promote the densification of glass/alumina composites. In the composite around 800°C, non-spherical pores, which remain after incomplete sintering, were observed. Above 900°C, the pores were spherical. During firing, several gases evolved from borosilicate glass in glass/alumina composites. The result suggests that these gases are dependent on the formation of the spherical pores.

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An expert system, which judges what kinds of perovskite-type mixed oxides will be formed in the ternary system of metallic elements, has been constructed as a part of a system for ceramic material design. In this system, formation was judged on the basis of crystallographic knowledge and databases which were collected from the literature: This system has two kinds of databases, all perovskites in the literature and ionic characters of elements. Conditions used to evaluate the stability of perovskites are, (1) charge balance, (2) ionic radius, (3) the stability of each ion and oxygen vacancy in perovskites, (4) stability of each ion of atmosphere, (5) acidbasicity, (6) the properties of d electrons of transition metals.

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In order to prepare a(1:1) complex perovskite compound for microwave dielectric resonators in the system CaO-Ga₂O₃-Ta₂O₅, phases present and microwave dielectric properties of the ternary dielectrics with various compositions near the stoichiometric cation ratio (4CaO⋅Ga₂O₃⋅Ta₂O₅) have been investigated. X-ray diffractometry combined with elementary analysis using WDX revealed that the dielectric materials prepared from a stoichiometric powder mixture of Ga₂O₃, Ta₂O₅ and CaCO₃ are composed of the intended Ca(Ga_1/2Ta_1/2)O₃ complex perovskite phase (CGT). It was also demonstrated that some other phases are formed in sintered samples with compositions different from the stoichiometric CGT ratio. The phase relation near the CGT composition is proposed, which contains newly obtained ternary (4CaO⋅2Ga₂O₃⋅Ta₂O₅) and binary (CaO-Ta₂O₅) compounds. A microwave high Q value of the CGT sample is found to be affected considerably by the secondary phases, with a pronounced deleterious effect by the binary compound. Additionally, some factors which might cause a marked decrease in the microwave Q value of the CGT sample on prolonged sintering are discussed in relation to structural evolution during sintering.

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The distribution of elements and the structure near grain boundaries in SrTiO₃ ceramics were investigated by using TEM, μAES and SIMS. TEM results showed that a secondary phase was formed at grain boundaries. Depth profiles of μAES showed that the concentration of strontium decreased in the region near the grain boundary, while that of bismuth and oxygen increased. The composition of the secondary phase was estimated to be Bi:Ti:O=2:2:7 with a small amount of Sr. The distribution of other minor elements was analyzed by SIMS. Bismuth ions were enriched at almost all grain boundaries, while that of manganese were reduced. Ca ions were always found together with Bi ions.

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Ba_0.99Sr_0.01Tio₃ ceramics were fired for 1 hour at a temperature from 1410° to 1460°C in H₂-N₂ atmospheres. A pure hexagonal phase, which was not formed by calcination in air, was obtained by firing for 1 hour at 1430°C in H₂ atmosphere. A part of the oxygen in Ba_0.99Sr_0.01TiO₃ was removed under the reducing condition, which led to the formation of the hexagonal phase. The amount of the hexagonal phase of Ba_0.99Sr_0.01TiO_3-x increased proportionally with an increase in oxygen deficiency (x). The value of x required for stabilizing the hexagonal phase at room temperature was found to be larger than 0.008. The transition temperature from cubic to hexagonal phase of Ba_0.99Sr_0.01TiO_3-x was higher than that of BaTiO_3-x, and oxygen deficiency required for stabilizing the hexagonal phase was larger than that for BaTiO_3-x. These results indicated that Ba_0.99Sr_0.01TiO_3-x does not easily transformed into the hexagonal phase.

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Optical or electron microscopes have been usualy used to observe ferroelectric domains. But they have some difficulties in applying an external electric field or in changing the temperature of a sample. A CCD microscope has been developed for the domain observation by combining a low magnification object-lens and a high resolution CCD sensor. The CCD microscope revealed more than ×1000 magnification on a CRT display with a very bright view. Moreover, it is easy to apply an electric field on the sample because of a sufficient distance between the object-lens and the sample. The image of the domain motion is instantaneously recorded with a VTR. Single crystals of the (1-x)Pb(Zn_1/3Nb_2/3)O₃-xPbTiO₃ system prepared by the flux method were used. This solid solution system exhibits a morphotropic phase boundary between rhombohedral and tetragonal phase near x=0.1. The phase transition behavior from ferroelectric to paraelectric phase becomes sharp with increasing PbTiO₃ concentration (x) in comparison with a diffused phase transition in Pb(Zn_1/3Nb_2/3)O₃. Our observation demonstrated that the ferroelectric domain motion is closely correlated with the phase transition diffuseness and dielectric relaxation.

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The ferro-to-paraelectric phase transition was investigated with a special interest in the diffuse phase transition in BaTiO₃-BaZrO₃ solid solutions, which was characterized by the gradual change of the relative dielectric constant with temperature. In the diffuse phase transition, the change in the relative dielectric constant with temperature was not directly associated with the change in a crystal structure. The Curie temperature, at which the relative dielectric constant took a peak value, appeared in the solid solutions with cubic symmetry. The cubic-to-rhombohedral transition occured gradually at a temperature below the Curie temperature. The present experimental data could not satisfactorily be explained by the statistical compositional fluctuation model in solid solutions.

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Temperature dependence of resistivity of SnO₂ single crystal thin films deposited on the c-surface of BaTiO₃ single crystal slabs has been investigated by theoretical and computer analysis. The dependence can be stabilized by the local states to establish the equilibrium state by electron transfer mechanism without resort to mass transfer. When temperature exceeds the Curie point the resistivity jumps up or down depending on the substrate polarity. When the potential channel is pinched off, the magnitude of resistivity jumps caused by the polarization disappearance and polarity reversal depends on the film thickness and density of bulk donors.

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Dielectric properties of ceramics in the system Pb(Zn_1/3Nb_2/3)O₃-SrTiO₃ that contained Pb(Cu, Mn, Nb)O₃ were studied. Comparing with Pb(Zn_1/3Nb_2/3)O₃-SrTiO₃ binary system, temperature coefficient of dielectric constant decreased by incorporating Pb(Cu, Mn, Nb)O₃. This is probably because the atomic species forming perovskite increased then the phase transition of dielectrics got more diffused. Cu¹⁺ emphasized this effect than Cu²⁺ or another atoms. Furthermore, we found Cu or Mn promoted aging of dielectrics and changed the temperature dependence curve of dielectric constant to a double peak. The ceramics developed in the system Pb(Zn_1/3Nb_2/3)O₃-SrTiO₃-Pb{(Cu_1-xMn_x)_1/3Nb_2/3}O₃ had a high density and a high resistivity when fired in atmospheres of low oxygen partial pressure below 1000°C. The ceramics had a high dielectric constant (>4000), a small temperature coefficient of dielectric constant (within 10% between -25° and +85°C when standardizing at 20°C; meeting YB specification of JIS), and a smaller change rate of dielectric constant under DC bias voltage than conventional BaTiO₃. The ceramics obtained are useful as dielectrics for multilayer ceramic capacitors with copper internal electrodes.

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Microwave dielectric properties of solid solutions in the system ZrTiO₄-HfTiO₄ were measured for quenched and slow-cooled specimens. The relative permittivity of the quenched specimen decreased with increasing Hf content; however, that of the slowly cooled specimen had a peak permittivity value for the composition containing 75mol% of ZrTiO₄. These results were almost identical with those reported at 1kHz. A specimen with a zero temperature coefficient of resonant frequency was obtainable by optimizing the composition and heat treatment.

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The grain size dependence of lattice constants (a and c), dielectric constant (ε/ε₀), dissipation factor (tanδ), electromechanical coupling factors (κ_t and κ_p), and mechanical quality factor (Q_M) was investigated in ceramics with the compositions of 0.99⋅Pb_1-XLa_2X/3TiO₃+0.01⋅MnO₂ with X=0.05 (grain size=0.37-1.32μm) and X=0.10 (grain size=0.30-1.14μm). With decreasing grain size, c/a (lattice constant ratio), tanδ (of non-poled), κ_t/κ_p (anisotropy of coupling factor), and Q_M decreased, while ε/ε₀ (of both non-poled and poled) increased. When poled, tanδ showed little grain size dependence. A close correlation was observed between the lattice constant ratio and the dielectric constant for all the materials, and the grain size dependence of these properties has been attributed mainly to the effect of internal stress in grains. The grain size dependence of tanδ may be interpreted on the basis of the effect of grain size on the motion of do-main boundaries. The values of Q_M^-1 and tanδ did not agree with the relationship, Q_M^-1∝tanδ, usually observed in ferroelectric materials. This is possibly explained in terms of the ceramic structure-dependent component of inner friction (Q_M^-1), which becomes significant with decreasing grain size.

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The dielectric composition BaTiO₃-Sr₂Bi₄Ti₅O₁₈ fired at 1000°-1050°C has excellent C-V characteristics and a high insulation resistance at 125°C. The composition 95mol% BaTiO₃-5mol% Sr₂Bi₄Ti₅O₁₈ exhibits a 1800 relative dielectric constant, a 1.0% dissipation factor and so weak temperature dependence of capacitance that designates EIA (Electronic Industries Association)-X7R. The fracture surface of the multilayer ceramic capacitor (MLCC) using this dielectric composition and 70Ag/30Pd internal electrode shows grain boundaries between the internal electrodes, while that of this dielectric body itself does not show. Consequently the insulation resistance of the MLCC fired at air atmosphere degraded in the accelerated humidity load test. The use of Pt for the electrode at MLCC is effective to prevent the influence of Ag/Pd on the dielectric body. It is found even if electrode is formed with 70Ag⋅30Pd material, when the MLCC is fired in weak reducing atmosphere, the above influence of the metal on the dielectric body is prevented.

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Porous SrTiO₃ ceramics containing an MgO-TiO₂-SiO₂ compound, Nb₂O₅, ZrO₂, and a perovskite compound of Mn, Cu or Co oxide, were prepared. After fired in air, the ceramics were reduced in an N₂-H₂ atmosphere and then oxidized in air at a temperature between 800° and 1200°C. Grain boundaries were mainly oxidized by the heat treatment and the ceramics exhibited the characteristics of both capacitor and varistor. The apparent value of effective dielectric constant ε decreased with the rise of temperature of heat treatment, and the maximum value 14 of nonlinear exponent α was obtained by the heat treatment at 1000°C. It is concluded that oxygen diffused through pores formed at tripple grain junctions, and oxidized the grain boundaries, thus furnishing the ceramics with the characteristics of capacitor and varistor.

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Relation between PTC (Positive Temperature Coefficient) effect and oxygen adsorption in porous BaTiO₃ ceramics was investigated. The semiconducting samples were prepared by reduction of sintered body in 50% H₂-Ar atmospheres followed by gradual reoxidization in air. The magnitude of the PTC effect increased with increasing reoxidizing temperature. Barrier height, which was estimated by taking Arrhenius plots of resistivity above Curie temperature, showed a similar tendency to PTC effect with the reoxidizing temperature. This barrier height is thought to be generated by chemisorbed oxygen on BaTiO₃ grain surfaces and to determine the PTC effect. The behavior of the adsorbed oxygen was confirmed by means of ESR at room temperature. ESR spectra indicate that the chemisorbed oxygen exist as O₂^-. ESR intensity assigned to O₂^- became stronger with increasing reoxidizing temperature. It seems that low-temperature type of the chemisorbed oxygen O₂^- contribute to formation of energy barrier.

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The degradation mechanism in PTC barium titanate ceramics under reduced atmospheres was investigated by the new method developed by authors. It was found that the potential barrier height in the lower temperature region (120°-180°C) was not affected by the degradation treatment, and that the height in the higher temperature region was reduced with the degradation time. It was suggested that the dominant factor in the degradation mechanism was the broadening of the distribution of interface states.

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Lead zirconate-lead titanate ceramics, Pb(Zr_yTi_1-y)O₃(PZT), are very important piezoelectric materials, because the piezoelectric ceramics near the morphotropic phase boundary (M. P. B.) show very large piezoelectric activities. However, the temperature dependence of the frequency constant and the electromechanical coupling factor of these materials in the vicinity of the M. P. B. indicate complex behavior, because of the minimum Young's modulus at the M. P. B. Stable temperature dependence of frequency constant is desired for piezoelectric ceramic devices such as ceramic filter, actuator, and so forth. In the PZT system, the M. P. B. has a slight tilt to the PbZrO₃ side and the degree depends on the ratio of the modified A site ions. The tilt of the M. P. B. was used to improve the temperature dependence of frequency constant of the piezoelectric ceramics with composition near the M. P. B. without decreasing the high value of the coupling factor. In this work, (Li_0.5Bi_0.5)-modified PZT system, (Li_0.5Bi_0.5)_xPb_1-x(Zr_yTi_1-y)O₃(PZT100x/100y), was selected. The improved ceramics have high coupling factors of more than 60%, from room temperature to 120°C. The temperature coefficient of the frequency constant in the planar mode is -16ppm/°C at 30°C, smaller than that of the conventional PZT ceramics.

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Multilayer piezoelectric actuator was manufactured the bonding method. This method had the advantage of low cost, since silver can be used for internal electrode. The bonding condition of 900°C between electrode and piezoelectric ceramics was suitable for the desired mechanical strength and electrical characteristics. This multilayer piezoelectric actuator was characterized by the high K₃₃, and by displacement of 2.5μm at 100V, which was in good agreement of original ceramics in itself.

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A new type of piezoelectric actuator was developed. This piezoelectric actuator consists of three layers: a piezoelectric ceramic layer, a middle layer whose composition changes gradually, and another ceramics layer with a high dielectric constant. This type of material is called Functionally Gradient Material (FGM). Two green sheets made from two different materials were laminated and sintered monolithically. The compositions of these two different ceramics were selected from the system Pb(Ni_1/3Nb_2/3)O₃-PbZrO₃-PbTiO₃. The bending displacement is about 60μm, at 100V applied at room temperature. The size of the plate (L×W×t) is 25×5×0.65mm³. An attempt was made to prepare a 3-dimensional FGM piezoelectric plate using a dispenser with a computer controlling the XY-stage. This equipment can change the distribution of the composition along the plane and across the thickness direction. An FGM piezoelectric plate that has a periodic structure (A on B vice versa alternating side by side repeatedly) is made by this equipment.

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Shape memory unimorph actuators have been trial manufactured using lead zirconate-based antiferroelectric ceramics (Pb_0.99Nb_0.02[(Zr_0.6Sn_0.4)_1-yTi_y]_0.98O₃). In a unimorph structure a slightly higher Ti concentration y(0.0630) is required than that (0.0625) in a simple disk, in order to stabilize the field-induced ferroelectric state; this is probably due to the compressive stress generated in the unimorph configuration. Dynamic response has also been investigated in the shape memory unimorph. Only a short period electric field pulse (<5ms) can drive the unimorph; this gives much advantage in controlling than in the conventional piezoelectric actuators.

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The variation of the Weibull modulus (m) of dielectric strength (E_b) with temperature showed that E_b scatters more widely in the ferroelectric phase than in the paraelectric phase or around the Curie point (T_c). This result was correlated to the fact that the variation of E_b was approximately inverse to that of dielectric constant. It was also found that the modules m varied with sintering conditions; a higher value of m (ca. 10-15) was obtained in a specimen sintered at a lower temperature for a shorter time. This result is probably correlated with the distribution of larger grains.

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Li₂B₄O₇ films, promising films for surface acoustic wave devices, were prepared by the sol-gel method using constituent metal alkoxides as starting materials. Li₂B₄O₇ films highly oriented along (122) plane were obtained on silicon (100) and (111) single crystal substrates when acetic or hydrochloric acid was added to the coating solution, while no orientation was observed without acid.

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Barium isopropoxide, lead naphthenate and titanium isopropoxide were mixed into a homogeneous solution. The homogeneous solution was spin-coated on silicon substrates and the obtained films were fired at 800°C in O₂. The dielectric constant of the films depended on the Ba/Pb molar ratio. Maximum value, which was 300, was obtained at Ba/Pb=50/50. The dielectric constant of the films were different from those previously reported for the bulk materials. This seems to be caused by the existence of the residual stress which was derived from the difference of thermal expansion coefficient between the films and the Si substrate. The fluctuation of the composition (Pb/Ba ratio) in the film was observed in (Ba, Pb)TiO₃ system by SIMS analysis. This fluctuation seemed to have occurred because barium alkoxide was more reactive to water than lead naphthenate.

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(1-x)PbTiO₃-xMgTiO₃ metastable solid solutions with x up to 0.5 were prepared by heating alkoxy-derived gels at 773K for 24h. X-ray diffraction analysis reveals that the perovskite solid solutions were obtained as a tetragonal structure when x<0.2, and as a cubic structure when 0.2≤x≤0.5. Dielectric measurements for the pressed powders show that no dielectric peak due to a ferroelectric phase transition was observed for the solid solutions. Both dielectric constants and dielectric losses decreased with increasing Mg content.

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The grain-oriented PZT ceramics were fabricated by tape-casting method using powders synthesized by a hydrothermal reaction, and the piezoelectric properties of ceramics were measured. Cyclohexanone was the most suitable solvent from the view point of dispersion of PZT powder in a slurry, and the addition of 100mg/g-PZT of an acrylic binder was necessary for disperson and strength of the tape before sintering. It was possible to fabricate green tapes in which PZT grains having a cubic shape were oriented along a- or c-axis. However, the degree of grain-orientation decreased considerably by sintering. The electromechanical coupling factor (k₃₁) and piezoelectric constant (-d₃₁) of the grain-oriented PZT ceramics were about 10% higher than those of ceramics fabricated by an ordinary procedure using a hydrothermally synthesized powder.

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Well-crystallized polycrystalline barium titanate thin films have been prepared at sufficiently low temperatures by the hydrothermal-electrochemical reaction on titanium-deposited glass substrates. The reaction was carried out in 0.1-0.5N Ba(OH)₂ solutions at temperatures of 100°-200°C and under saturated vapor pressures, using a titanium-deposited glass substrate for anode and a Pt plate for cathode and applying an electric current galvanostatically up to 18mA/cm². The BaTiO₃ film was lustrous and dense. The thickness of the film estimated from the weight change increased from 70 to 300nm with treatment time from 10 to 60min at 200°C in 0.5N Ba(OH)₂ solution with the current density of 15mA/cm². The adhesion of the BaTiO₃ film to the glass substrate was so strong that no exfoliation was observed. Similar BaTiO₃ thin films with thickness less than 70nm were formed under hydrothermal conditions without electricity.

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Sintering behavior, crystallographic structure and dielectric properties of the nonstoichiometric Ba_(1-X)(Zn_1/3, Ta_2/3)O₃ with 0≤X≤0.04 complex perovskite system were investigated. The sintered density was improved by reducing Ba concentration. The degree of Zn and Ta ordering and lattice distortion were promoted by reducing Ba concentration. It was assumed that these phenomena were caused by lattice defects ascribed to nonstoichiometric structure. As a result, at X=0.01, Q value reached above 13000 (at 10GHz) with sintering for 4h; however, above X=0.01, Q value was greatly decreased, in spite of saturation in Zn-Ta ordering.

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The relationship between the electrical conductivity of BaTiO₃ ceramics and sintering time was studied. SiO₂ (2wt%) and La₂O₃ (0.02wt%) were added to a mixture of BaCO₃ and TiO₂, and sintered at 1300°C for 1 to 10h in an oxygen atmosphere. With an increase in sintering time the electrical conductivity decreased, and the PTC effect became less evident. AC conductivities also decreased with sintering time, and showed a maximum value at the temperature at which PTC effect was observed in DC conductivity measurement. These experimental results can be explained by the change in trap density at the grain boundaries above and below the crystal transition point.

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The effect of SiO₂ on the electrical conductivities of BaTiO₃ was studied. From 0.5 to 3.5wt% of SiO₂ was added to BaTiO₃, and the mixture was sintered at 1300°C for one hour. Specimens containing 0.5 to 3.0wt% SiO₂ had an average grain diameter of 30μm and the electrical conductivity of 10^-2S/m at room temperature, and showed PTC effect. On the other hand, specimens containing 3.5wt% SiO₂ had an average grain diameter of 3μm and low electrical conductivity of 10^-11S/m at room temperature, and did not show PTC effect. Thus, electrical properties depend on the SiO₂ content, and these experimental results were explained by changes in the average grain diameter of the sintered BaTiO₃.

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A new type quartz piezoelectric sensor coated with a sputtered Pt film was proposed for the detection of inflammable gases, i.e., H₂, CO, and iso-butane diluted with air. The sensing signal of the new sensor is provided by an increase in resonance frequency of the crystal (ΔF) due to a temperature increase upon contact with sample gases in the temperature range 100°-400°C. The frequency change of the sensor was found to be opposite in direction to that of a conventional adsorptiontype piezoelectric gas sensor operating at ambient temperature. The temperature change of the present sensor resulted from the oxidation of the inflammable gas on the surface of the catalyst film. A linear relationship between ΔF and H₂ concentration (0-0.4vol%) was observed at the temperatures examined. The 90% response time of the present sensor to 0.3vol% H₂ was about 20s at 200°C. The sensitivity of the sensor to H₂ in air increased sharply with increasing temperature above 100°C. Furthermore, the gas selectivity to H₂ was very high especially at 100°-200°C.

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