The design and fabrication of textured bulk polycrystals have been one of the key issues for ceramists in their effort to extract the best performances from functional materials through powder processing. Reactive-templated grain growth (RTGG) is a processing method in which reactive template particles are mixed with complementary reactants and aligned, and the product is formed in-situ during heat-treatment, preserving the orientation of the template. RTGG has been applied to simple perovskite-type materials, yielding highly textured polycrystals with enhanced piezoelectric properties. The proposed method has also been extended to layer-structured materials, including bismuth layer-structured ferroelectrics and both p- and n-type oxide thermoelectrics with complex compositions. The optimum combination of microstructural and compositional designs is expected to produce outstanding materials with superlative performances.

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Highly microstructure controlled ceramics are required for improving their properties. Colloidal processing using fine particles provides this required control mechanism through a well-dispersed suspension or hetero-coagulate suspension. As a merit of colloidal processing, the preparation of superplastic zirconia is demonstrated using sub-micronsized powders. Highly microstructure controlled ceramics fabricated by a novel colloidal processing were demonstrated as follows: (i) dense nano-sized zirconia without pressure sintering, (ii) porous ceramics with controlled pore size by hetero-coagulated suspension of ceramics and polymer, and (iii) textured ceramics with feeble magnetic susceptibility by colloidal processing in a high magnetic field.

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The ceramic industry uses enormous amounts of energy to make products at high temperatures. Therefore energy-saving measures based on sintering process improvements are being examined. Barium titanate in the presence of a liquid phase was irradiated by two different methods during microwave sintering: an intermittent use of the same high power levels (time-control method) and a continuous use of lower, increasing levels of power (power-control method). As a result, it is concluded that the liquid phase is generated faster in the time-control method provided that the microwave irradiation is carried out at a temperature which is higher than the generation temperature of liquid phase. The liquid phase was generated at a wider temperature in the power-control method. It has been understood that the temperature control becomes difficult, though the time-control method is more efficient for energy efficiency.

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The high-temperature dimensional stability of β-spodumene solid solution (s.s.) glass-ceramics with different crystallinities was investigated. It was demonstrated that the glass-ceramics show volume change due to structural relaxation in the residual glass phase regardless of crystallinity, even in the specimen with a high crystallinity of 90 vol%. The volume change process was expressed by the Kohlrausch-Williams-Watts (KWW) function. In the specimens with lower crystallinity (52, 71 vol%), normal relaxation behavior like that of non-crystalline glasses was observed, with activation energies of 599 and 414 kJ/mol, respectively. In contrast, the specimen with a crystallinity of 90 vol% showed an anomalous relaxation behavior accompanied with a densification limit and lower activation energy (250 kJ/mol). This anomalous behavior was attributed to the inner friction caused by proximity of the crystal grains in the glass-ceramic, which may result in a blocking effect on the volume shrinkage. We predicted the long-term dimensional stability of a precision glass-ceramic capillary for fiber-optic devices, based on the relaxation data in the KWW function.

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Grain size and piezoelectric properties were investigated in (K, Na)NbO₃ ceramics substituted with Ba for K and Na by 1 to 5 mol%, in anticipation of high piezoelectric properties. The grain size strongly depended on the A/B ratio in perovskite structure. The grain growth phenomenon was markedly similar to that of BaTiO₃ semiconducting ceramics with donor additives. Piezoelectric properties were strongly affected by grain size. MnO additive was added to suppress grain growth anomaly, dense ceramic body formation and withstanding voltage enhancement. However, a manufacturing process, in which MnCO₃ was directly mixed to other raw material powders, resulted in the formation of large pores ranging to 1 mm diameter in their ceramic bodies. The powder obtained by previously calcining the mixture of Nb₂O₅ and MnCO₃ was used as a raw material for MnO addition, in order to prevent the formation of large pores. By adding 0.5 mol% MnO, grain growth anomaly was inhibited, and a uniform and dense ceramic body was consequently obtained without piezoelectric property degradation.

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A recycling process was developed for barium titanate based waste material, which is produced in the large scale industrial production of ceramic capacitors and related devices. Barium titanate powder was first dissolved in a concentrated aqueous HCl solution, followed by dilution with water and heating to 100°C, which resulted in the precipitation of a white crystalline titania powder. The crystalline phase of the prepared titania can be controlled by the preparation conditions, i.e., heating rate, and this process successfully produced pure anatase powder with good photo-catalytic activity. The barium ion, another main component, was also separated as barium sulfate by a simple precipitation process.

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A fluorescent substance is a material that emits light over a period of time, after being excited by optical energies, such as sunlight or a fluorescent lamp. The preparation of fluorescent material made by using SrCO₃ and Al₂O₃ is well known. However, the preparation of the fluorescent material made using Sr(OH)₂ and Al(OH)₃ is not so well known. We aimed at the composition of a fluorescent substance that used Sr(OH)₂ and Al(OH)₃ as starting materials in this experiment. Moreover, a comparison of the characteristics of samples that used hydroxide for starting materials, and those produced using SrCO₃ and Al₂O₃ was performed. It was found that the sample using the hydroxides as starting materials was easily synthesized. Also, the fluorescent characteristics of the sample that used the hydroxides were better than the samples that used SrCO₃ and Al₂O₃.

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We have investigated the influence of the excess doping of alkaline earth oxides on the structure and electrical conductivity of the Ba_xSr_yLa_0.50InO_2.25+x+y (x+y≧0.5) system. It was found that over 0.10 mol of BaO or SrO could be doped in 1 mol of the cation stoichiometric system (x+y=0.50). We propose that some of the Sr cation move from A-sites to B-sites in this system to maintain the cation stoichiometry [(x+y+0.50) : In=1 : 1]. The dependence of the electrical conductivity on the oxygen partial pressure varied with the magnitude of the oxide ion conductivity. The oxide ion conductivity of the excess-doped system was dependent on the unit cell free volume. The relationship corresponded to that of stoichiometric Ba_xSr_yLa_0.50InO_2.25 (x+y=0.50) and Ba_1-yLa_yInO_2.50+y systems.

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It is important to find a possibility for utilizing coal-preparation refuse (CPR) generated from coal mines in terms of environmental and economic points of view. In this study, a possibility for manufacturing fired clay bricks (FCBs) by CPR instead of clay was investigated. Firing shrinkage ratio, compressive strength, and water absorption ratio of test samples manufactured using CPR in the open air were measured. It was found that firing shrinkage ratio and compressive strength decrease with increasing the addition amount of CPR, while water absorption ratio is almost constant under the entire addition amount ranges of that. The test sample manufactured was nearly similar to the 1st grade clay bricks of Korea Standard L (ceramics) 4201.

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We developed a foaming water glass (FWG), a kind of alkaline sodium silicate hydrate (lNa₂O•mSiO₂•nH₂O) and applied it to a HCl remover and a dioxin inhibitor in flue of waste incinerators. HCl emissions from PVC (polyvinyl chloride) proved to decrease substantially by incinerating the PVC with the FWG, indicating that the FWG is a useful HCl remover. HCl concentrations in flues of industrial waste incinerators were also reduced with larger efficiency than the conventional calcium hydroxide particles by injecting a diluted FWG solution as a cooling water. The reduction of HCl generation led to the decrease in dioxin concentrations in flue gas and fly ash.

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Zirconium oxide thin films were fabricated using a sol-gel method. The sols were prepared using zirconium alkoxide and acetate. An alcoholic solution of the alkoxide and an aqueous solution of the acetate were dip-coated on a glass substrate and fired at 600°C. Both films were crystallized as the tetragonal phase, which was detected by an XRD and an electron beam diffraction of an ion-thinned section. On the other hand, the electron beam diffraction of the thin section of the film prepared by crushing in a mortar, exhibited the monoclinic phase, which was transformed by stresses applied during sample preparation for TEM. The SEM observation showed a grain size of 30-50 nm. The TEM micrographs exhibited contrasts of less than 10 nm size in a single grain of about 30 nm.

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The surface of six different grades of commercial sub-micron high purity α-Al₂O₃ powders produced by two different processes, in-situ chemical vapor deposition (“A” powders), and hydrolysis of aluminum alkoxide (“B” powders) methods, were evaluated by temperature programmed desorption mass spectrometry (TPDMS) and diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. Desorption of CO₂ molecules was detected for all the powders, but the quantity was greater for the “B” powders than the “A” powders. The maximum of the CO₂ desorption peak was in the range of 230-270°C for all powders. The desorbed CO₂ peak was considered to evolve from adsorbed CO₂ molecules forming hydrogen carbonyl groups through interaction with the Al^IV-OH groups on the α-Al₂O₃ surfaces. The DRIFT spectra of the powders heated at 700°C under vacuum confirmed a larger population of Al^IV-OH groups on the surface of the “B” powders. The present study clearly demonstrates the presence and quality of the Al^IV on the surface of α-Al₂O₃ powders and the effect of the type of manufacturing process on their proportion.

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The synthesis of nano crystalline particles of cerium oxide at room temperature was investigated in detail. Highly crystallized cerium oxide nano powder with a particle size of 10 nm was obtained by adding a hydrazine aqueous solution or an ammonia aqueous solution into a cerium nitrate solution followed by stirring the mixed solutions over a prolonged period at room temperature. It was considered that the good crystallinity was attributable to the use of an aqueous solution containing Ce(III) ions as a starting solution.

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Monolithic polycrystalline zeolites with through-macropores were prepared by steam treatment of bimodal porous silica gel monolith in the presence of tetrapropylammonium hydroxide, where the bimodal porous silica gel was prepared by inducing phase separation during sol-gel process. The silica skeleton with mesopores was transformed into polycrystalline zeolites maintaining continuous macropore morphology and monolithic shape. In the zeolites, there are three different pores arranged hierarchically: through-macropores originally existed in the precursor silica gel, small macropores at interstitial of zeolite crystallites, and micropores in zeolite framework.

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