This paper reviews technical advantages of a layered ceramic resonator for a highly stable frequency standard, and its application to lead free piezoelectric ceramic materials such as SrBi₂Nb₂O₉ (SBN). Characteristics of typical three single-plate-type thickness mode resonators; the fundamental thickness shear (TS1) mode resonator, the fundamental thickness extensional (TE1) mode resonator, and the third harmonic thickness extensional (TE3) mode are also briefly described as a stable frequency standard for comparisons to the layered ceramic resonator, which utilizes the second harmonic thickness extensional (TE2) mode vibration. This paper also describes the advantageous characteristics of SBN as a ceramic material for the resonator applications.

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Three-dimensional vinyl-functionalized silica colloidal crystals (VFS-CCs), which the attenuation of the photonic bandgap could be significantly improved by thermal annealing, were fabricated by a gravity sedimentation process using monodisperse vinyl-functionalized silica spheres. With the increase of the annealing temperature from 60 to 140°C, the attenuation of the bandgap had more than 40% increase. The SEM images and optical UV–vis–NIR spectra confirmed the high quality of the VFS-CCs. Fourier transform infrared (FT–IR) spectra and thermo-gravimetric analysis (TGA) of the vinyl-functionalized silica spheres demonstrated that the optimal annealing temperature of the VFS-CCs was about 120°C, slightly lower than the oxidation temperature of the vinyl groups. This work provides a simple and controllable method for fabricating and optimizing the optical properties of the surface-modified colloidal crystals.

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In this paper, pure and w-doped VO₂(A) nanorods were synthesized via the reduction of V₂O₅ with oxalic acid through hydrothermal treatment and characterized by XRD, SEM and DSC. The study about the influence of w-doping on its phase transition and stability properties was carried out for the first time on the best of our knowledge. The doping of tungsten decreased the phase transition temperature of VO₂(A) just as it does in the case of rutile VO₂(R). The doping limitation of tungsten for pure VO₂(A) was estimated to be about 0.5–0.75 at. %, whereas over doping of tungsten led to the destabilization of VO₂(A) phase. Based on the experimental results, the solution reaction process should be such that VO₂(B) was first formed at lower temperature or shorter time, and then transformed to VO₂(A) or VO₂(R) during hydrothermal treatment. Furthermore, inhomogeneous doping of tungsten in VO₂ during the crystallization from the solution was revealed by DSC measurements.

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A powder mixture of Ti, Al₄C₃ and graphite was adopted to synthesize a new TiC/Ti₃Al/Ti₂AlC composite by spark plasma sintering. The reaction route was proposed from XRD analysis. TiC, Ti₃Al and Ti₂AlC formed from 800°C with TiC_x and Ti₃Al_y acting as the intermediate phases until the reaction process completed at 1200°C. It was found from TEM observation that Ti₃Al underwent an intergrowth relationship with TiC grains inside the Ti₂AlC matrix due to the in situ reaction sintering. The average hardness, fracture toughness, Young’s modulus and bending strength of the composite were 10.2 ± 0.6 GPa, 6.5 ± 0.2 MPa·m^1/2, 436 ± 11 MPa and 227 ± 13 GPa, respectively.

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A SrTiO₃ hetero-nanostructure was synthesized via solvothermal reaction using a protonated trititanate nanowire (H₂Ti₃O₇) and strontium hydroxide octahydrate (Sr(OH)₂·8H₂O) in an ethanol/water mixed solvent system. The ethanol to deionized water volume ratio was the controlling parameters for determining the phase formation and the particle size of the SrTiO₃ nanocrystals. Single-phase cubic perovskite SrTiO₃ began to form at 120°C in a mixed solvent containing >40% ethanol by volume. Field emission scanning electron microscopy (FE-SEM) and high resolution transmission electron microscopy (HRTEM) showed that the as-prepared SrTiO₃ retained its wire-like (1D) morphology with nanocrystals (0D) on the surface. The synthetic mechanism of the 0D-1D SrTiO₃ hetero-nanostructures was demonstrated by topochemical reaction from dielectric tuning of the mixed solvent and the correlation between the crystal structures of SrTiO₃ and H₂Ti₃O₇. Using as-prepared SrTiO₃ nanowires, the photocatalytic activity for the degradation of a rhodamine B dye solution was evaluated under UV irradiation and compared to SrTiO₃ powder from solid state reaction.

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(Ba_1−xCa_x)_m(Ti_1−yZr_y)O₃ (BCTZ-x-y-m) ceramics were studied to clarify the effects of Ca and/or Zr addition and the non-stoichiometry of BCTZ ceramics. The range of each element was 0.00 ≦ x, y ≦ 0.25 and 0.995 ≦ m ≦ 1.02. All powders were prepared by a solid state reaction method. Green bodies with disc shapes were sintered at 1500°C for 2 h in air and then reheated at 950°C for 5 h in various reducing conditions. The dielectrics with the substitution of Ca ion in BCTZ-x-0.0-1.01 (x ≦ 0.10) showed an increase in T_c and the insulation resistivity improved with increasing x. The increase of Zr content (y) in BCTZ-0.1-y-1.01 and m in BCTZ-0.1-0.1-m led to the phase transition of dielectrics to relaxors, accompanying the decrease of T_c. In BCTZ-0.1-0.1-m, Ca and Zr co-doped dielectrics showed a high insulation resistivity (IR), even though m = 1.00. There are two possible origins of the higher resistivity observed in BCTZ with m = 1.0. The first is the acceptor action of Ca ions that moved from Ba sites to Ti sites in BaTiO₃; the second is the higher charge stability of the Zr ion than that of the Ti ion in a reducing atmosphere.

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Ceramic tiles are one of the most widely used materials in both commercial and residential buildings. As environmental problems increase, the need for environment-friendly building design increases. To achieve this, architects and engineers need reliable data on the environmental impacts of various building materials—including ceramic tiles. This paper reports the results of environmental impact assessment of ceramic tile production in Thailand. Key impact categories, including fossil fuel impact, global warming, ozone depletion, ecotoxicity, and human toxicity were assessed. The results showed that when assessed by EDIP methodology, the global warming impact value of 3.73E+3 kg CO₂-eq per megagram (Mg) of ceramic tile is quite prominent and is rather high compared with existing data in current literature. The human toxicity impact value is also significant. The values of the other impact categories were also determined and found to be relatively high. When assessed using the Eco-indicator 99 methodology, the results showed that the fossil fuel category was the most affected with a value of 8.62E+1 Pt per Mg of ceramic tile, followed by respiratory inorganics and climate change. Raw materials transportation stage yielded the highest environmental impact values. It is thought that the key factors responsible for the relatively high impact values are the process technologies employed and the long transportation distances of the raw materials. It was concluded that the environmental impact values of ceramic tile production in this study are different from, and in most cases higher than, the values presented in current literature.

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Electric conductivities of Zn_2−x/2Ti_1−xTa_xO₄ have been measured at 900°C in the oxygen partial pressure range of 1 to 10⁻¹³ atm, in order to estimate the ionic conduction separately from the electronic one. The obtained ionic conductivities were in good agreement with the products of electric conductivities and t_ion by oxygen gas concentration cells, which grew exponentially with the cation vacancy concentration in this system. Dielectric relaxation experiments on Zn_{2−(x−y)/2}Ti_1−(x+y)Ta_xAl_yO₄ system revealed that ionic diffusion process varied gradually from the oxide ion vacancy mechanism to the interstitialcy diffusion with increasing extrinsic cation vacancy concentration.

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(Bi_0.5Na_0.5)TiO₃ (BNT) dense ceramic films with a thickness of approximately 25 µm were deposited by an aerosol deposition method, and thieir ferroelectric and leakage current properties were investigated. The BNT films annealed at 1100°C represented the leakage current density (J) of 10⁻⁶ A/cm², while the BNT films annealed at 800 and 1000°C led to a marked decrease in J. The J of order of 10⁻⁷ A/cm² was obtained for the films annealed at 1000°C. The ceramic films annealed at 1000°C showed a remanent polarization (P_r) of 27 µC/cm² which was larger than that of the ceramic films annealed at 800°C (a P_r of 7.4 µC/cm²).

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Ceramics will be widely used for enhancing the efficiency of power generating systems, particularly gas turbines. However, ceramics used in these systems suffer damage owing to impact by foreign objects. In this study, various ceramic plates are impacted by a spherical projectile with an impact velocity of 320 m/s. The volume of the cone cracks formed on the plates decreases with an increase in the fracture toughness of the ceramic material. No cone cracks are formed on the zirconia (3Y-TZP) plate because crack formation is prevented by stress-induced phase transformation outside the impacted region. The volume of the cone crack is higher and the energy consumed by surface formation is smaller in transgranular-fractured ceramics than in intergranular-fractured ones. The fracture process can be controlled by controlling the characteristics of the grain boundaries, as well as by stress-induced phase transformation.

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The purpose of this paper is to design a Cymbal for harvesting energy from asphalt pavement. Asphalt pavement is used popular on road. Part of the energies in the pavement caused by vehicle and gravity can be harvested by piezoelectric transducers. Cymbal is selected to harvest energy from asphalt pavement because of its low cost, high reliability and reasonable efficiency. The efficiency and coupling effects with pavement of Cymbals with various sizes are discussed through finite element analysis (FEA). The displacement difference at pavement surface between with and without Cymbal is developed to considering the coupling effects. The results show that the potential electric energy harvested from pavement increases with the diameter of Cymbal. However, the efficiency decreases with the increasing of Cymbal size. The diameter at 32 mm is suggested as the size of Cymbal. The potential electric energy increases near linearly with the diameter of end cap cavity base. Enough bonding area should be left to bond the end steel cap and PZT. There is a maximum electric energy existing when the top diameter of the end steel cap changes. The maximum electric energy is generated when the thickness of cap steel is about 0.3 mm. There is also a maximum electric energy existing when the height of end cap cavity changes. The Cymbals with thicker PZT can generate higher electric potential and storage electric energy. Considering the storage electric energy, cost, bonding between end steel cap and PZT and the pavement surface displacement, the Cymbal with 32 mm of total diameter, 22 mm of cavity base diameter, 10 mm of end cap top diameter, 0.3 mm of cap steel thickness, 2 mm of cavity height and 2 mm of PZT thickness is suggested as the optimum one for harvesting energy from asphalt pavement. The electric potential is about 97.33 V of the design Cymbal. 0.06 J electric energy can be storage in that Cymbal. Its potential maximum output power is about 1.2 mW at 20 Hz vehicle load frequency.

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The influence of thermal annealing on the photoluminescence properties of the ZnSe-core/In₂O₃-shell nanowires prepared by a two-step process comprising the thermal evaporation of ZnSe powders and the sputter-deposition of In₂O₃ was investigated. The ZnSe nanowires were a few tens to a few hundreds of nanometers in diameter and up to a few hundreds of micrometers in length. Photoluminescence measurements showed that ZnSe nanowires had an emission band centered at around 630 nm in the orange region. In contrast, ZnSe-core/In₂O₃-shell nanowires had a stronger emission band centered at around 560 nm in the yellow-green region. The major emission of the ZnSe nanowires was found to be blue-shifted and enhanced in intensity by coating them with In₂O₃. The major emission is shifted back to 630 nm and further enhanced by annealing in a reducing atmosphere, whereas it is shifted back to ∼620 nm and degraded in intensity by annealing in an oxidative atmosphere. The PL enhancement by annealing in a reducing atmosphere is mainly attributed to the formation of In interstitials in the ZnSe cores during the annealing process.

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This paper correlated a convenient orientation index, Lotgering factor (LF), with the orientation distribution of a crystal-orientated polycrystalline material, theoretically and experimentally. For particle-oriented bismuth titanate (Bi₄Ti₃O₁₂) as a model, a Cauchy probability density function (CF) was valid for representing the orientation distribution of oriented material. The LF was calculated from XRD patterns which were derived from assumed orientation distribution. The standard deviation was used for the indicator of the LF with the orientation distribution. The non-linear relationship was found between them theoretically. This relationship was supported by the experimental data using particle-oriented bismuth titanate prepared by a magnetic field. The LF and orientation distribution of oriented bismuth titanate were obtained from the XRD patterns and the rocking curves, respectively. The result leads the LF to more convenient orientation index in relation to orientation distribution.

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In the templated grain growth (TGG) method for the grain-oriented ceramics, a method using single crystal particles with cubic shape as templates were investigated. The rolling-extended method was used to align the cubic templates to a direction in matrix. A cubic ceramic of 2 mm on a side was used as a pseudo cubic template, in order to observe the behavior of the cubic templates under the rolling extension. By the compressive deformation, the cubic ceramic turned its [111] direction to the compressive direction. Since the MgO single crystal particles are excellent in the cubic shape, they were selected as templates. The fabrication of [111] oriented MgO ceramics was experimentally investigated with the rolling-extended method.

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Highly luminescent Si nanoparticles (NPs) terminated with alkoxy monolayers have been synthesized via sodium biphenylide reduction of SiCl₄ encapsulated with inverse micelles of dimethyldioctylammonium bromide in a mixture of toluene and glyme, and subsequent alkoxylation of surface Si–Cl bonds. The optical absorption and emission spectra are blueshifted with reduction in size of the Si NPs (d ≤ 5 nm), relatively. Interestingly, it is found that the monolayers, which serve as a shell to protect the Si core from surface oxidation, play an important role in the appearance of the quantum size effect which generates a size-tunable photoluminescence (PL) property with a high PL QY. Decrease in molecular coverage of an alkoxy shell causes the partial surface oxidation of a Si NP, leading to the appearance of the interfacial-related PL feature. Time-resolved study of the fluorescence in Si NPs with and without oxide is performed to understand the essential difference of the electron–hole recombination process between each NP systems. The synthesis of highly luminescent NPs with tailored PL properties in the ultraviolet–visible region required full control of the NP size distribution and the chemical property at the heterogeneous interface between the Si cores and the organic shells.

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BaTiO₃ ceramics with different domain sizes were prepared by spark plasma sintering (SPS) and normal sintering (NS) using hydrothermally synthesized 100 nm and 500 nm powders. It was found that their piezoelectric constant d₃₃ shows great dependence on the size of ferroelectric domains. A high d₃₃ up to 416 pC/N was obtained in the SPSed ceramics derived from 100 nm powders, whose domain width was identified <50 nm by transmission electron microscopy (TEM). However, the d₃₃ values are 216 and 193 pC/N, respectively for the BaTiO₃ ceramics prepared by SPS using 500 nm powders and by NS using 100 nm powders, whose microscale domains can be observed by optical microscopy.

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In order to remedy defects of thin electrolyte films, which significantly affect the power generation performance of solid oxide fuel cells (SOFCs), the effects of pre-sintering of raw material powder (8 mol % Y₂O₃-stabilized ZrO₂: YSZ) on the properties of the electrolyte were investigated. After pre-sintering YSZ powder under various temperature and time conditions, electrolytes (about 30 µm in thickness) were deposited on the substrates of fuel electrodes by a dip-coating method and then co-sintered. The microstructures of the electrolytes were observed by scanning electron microscopy and laser scanning confocal microscopy. The power generation performance of fabricated cells was also investigated. As a result, the electrolyte fabricated by pre-sintering YSZ powder at 200°C for 120 h was found to be dense and impermeable. The cell containing the electrolyte showed reasonable power generation performance. In the case where the pre-sintering temperature was maintained at 200°C and the pre-sintering time was shortened to 20 h, the electrolyte was found to be porous, and the open circuit voltage of the cell was lower than the theoretical value. By increasing the pre-sintering temperature to 600°C for 20 h, an ideal electrolyte could be obtained. In contrast, the electrolyte fabricated using the YSZ powder without pre-sintering was highly porous, leading to a considerable drop in open circuit voltage.

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The purpose of this study is to form a film of dry-milled zirconia powders by aerosol gas deposition (AGD). Recently, we reported that we could form a high-density zirconia film using wet-type zirconia powders prepared wet-chemically. From the stand point of industrial use, the dry-milled zirconia powder seems to be much more advantageous than the wet type. In this study, we examined the possibility to fabricate zirconia film using commercially available dry-milled zirconia powders with a mean diameter range that is nearly the same as those of wet-type ones, for example, 0.73 to 10.2 µm in mean diameter. As a result, we were able to make a zirconia film from all powders, although the film formation conditions for the wet-type powder was very much limited in the diameter and the specific surface area. In conclusion, dry-milled zirconia powders are considered to have high potential for industrial use.

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Oxygen-enriched air has been expected to be used in several industrial processes for the purpose of less energy consumption as well as less CO₂ emission. Thus, an innovative and economical oxygen-separation method is eagerly needed for a large-scale production of oxygen-enriched air. Pressure-swing adsorption (PSA) method is considered to be effective for this purpose, if the high-performance oxygen adsorbents can be developed. It has been lately reported that La–Sr–Co–Fe-based perovskite-type oxide is a good candidate as a potential oxygen adsorbent for PSA. However, its cost is still relatively high, because the oxide is composed of relatively expensive elements of La and Co. Here, we compared the oxygen sorption behavior of the BaFeO_3−δ and SrFeO_3−δ samples which are composed of much inexpensive elements. These oxide samples were synthesized and then evaluated for oxygen sorption and desorption characteristics by the variation of oxygen partial pressure, with the simultaneous observation of change in crystal structure. As a result, it was found that the prepared BaFeO_3−δ and SrFeO_3−δ samples gave a relatively high amount of sorbed oxygen at lower (ca. 300°C) and higher (ca. 700°C) temperature, respectively. In addition, the reversible change in crystal structure associated with oxygen sorption/desorption was observed for both oxides at each best operating temperature.

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We investigated the crystallization and resulting morphology of a stoichiometric barium-silicate glass Ba₂Si₃O₈ (B2S3) using TEM observation and Raman spectroscopy. Spherical crystal growth (i.e., spherulite) of stoichiometric B2S3 phase was observed in the heat-treated glass samples, and the size of the spherulites drastically increased as the temperature increased during the heat-treatment process. It was also found that an initial precipitating phase in the precursive stage of crystallization is neither the B2S3 phase nor other crystalline phases in the BaO–SiO₂ system. It was deduced that a metastable phase precipitates prior to the formation of spherulite and acts as nucleation site for the spherulite.

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Microwave local heating was used to join silicon nitride. Glass was placed at the joint between two silicon nitride pipes and a silicon carbide susceptor was placed around the joint. The susceptor was locally heated by absorbing the microwave radiation. On heating to 1500°C, the glass melted and filled the space between the pipes, thereby joining the two pipes. Average strength of the specimen cut out from the joined pipe was 446 MPa. This demonstrates the potential of microwave local heating for joining silicon nitride.

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For the first time, vertically aligned carbon nanotubes (VACNT) were produced using waste cooking palm oil as green starting materials. The synthesis was carried out in a floating-catalyst thermal chemical vapor deposition reactor. Field emission scanning electron microscopy, energy dispersive X-ray, micro-Raman and thermogravimetric analyses, showed that the carbon nanotubes are of excellent quality, comparable to those obtained using conventional carbon sources. Under a typical synthesis condition of 5.33 wt % ferrocence as catalyst and a furnace temperature of 750°C, a mixture of single and multi-walled carbon nanotubes of 85% purity, vertically aligned on a silicon substrate, were produced. Field emission from the VACNT indicated reasonable turn-on field at 2.25 V/µm which corresponded to the current density of 10 µA/cm². The threshold field was observed to be about 3.00 V/µm at 1 mA/cm². The maximum current density of 6 mA/cm² measured was obtained for 4 V/µm. It is concluded that the VACNT from the reuse of waste material are suitable for applications in flat panel displays and flat lamps.

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