Zirconia-toughnened alumina(ZTA) powders that were uniformly coated with zirconia and yttria on the surface of alumina particles were prepared in order to inhibit the grain growth of alumina. Alumina particles were ultrasonically dispersed in the ethanol solution of Zr-n-propoxide, and then the Zr-alkoxide was hydrolyzed. Hydrated zironia as thin film was stabilized to tetragonal crystalline form by doping yttria as a stabilizer. The prepared ZTA powders had the good sinterability even at the lower temperature. As a result, the sintered bodies showed the enhanced fracture toughness compared with pure alumina. The relative density and fracture toughness(KIC) of the ZTA bodies sintered at 1550 were 98% and 5 MPam1/2 respectively.

The effect of heat-treatment temperature on the microwave absorbing properties was investigated in Ni0.8Zn0.2Fe2O4 specimens. The composite specimens were prepared by modling and curing the mixture of prereacted ferrite powder and silicone rubber. The measurement of complex permeability and permittivity was made by the reflection/transmission method. The most sensitive material constants with heat-treatment temperature is the imaginary (loss) component of permeability. The higher the heat-treatment temperature, the greater the magnetic loss. The composite specimens with high magnetic loss exhibited superior microwave absorbing properties. The quantitative estimation of microwave absorbing properties were made by plotting the observed material constants on the calculated solution map of impedance-matching.

The physical properties of 0.5PZT-0.5(PNN-PZN) ceramics have been investigated as a function of PZN content. A pyrochlore phase exists in the range of 600∼850 and a stable perovskite phase appears above 850. The piezoelectric properties (except electro-mechanical coupling factor) of 0.5PZT-0.5(PNN-PZN) ceramics showed almost linear relationships of PZN content within the range of 0.5PZT-0.5PNN system and 0.5PZT-0.5PZN system. The temperature dependence of piezoelectric constant, the electric field dependence of induced strain and a bend strength are improved by addition of PZN.

In order to grow a 127.86rotated LiNbO3 single crystal with good characteristics of surface acoustic wave (SAW) up to 80 mm in diameter, the temperature gradient of furnace, the growth rate and the rotation rate of crystal were changed. We could grow a crystal which had few macro defects at the conditions of temperature gradient as 30~6/cm, growth rate as 5 mm/hr and rotation rate as 8 rpm. The experimental ranges of the growth conditions are as follows. Temperature gradient was varied from 20 to 20/cm, growth rate as 5~7 mm/hr and crystal rotation rate as 6~12rpm.

It had been studied the structure and the magnetic properties of singel phase Co2Y(Ba2Co2Fe12O22) powder, one of the hexagonal ferrite. The material was successfully prepared by a commercially applicable coprecipitation method. Adding asqueous solution of BaCl2, CoCl2 and FeCl2(Ba2+:Co2+:Fe2+=1:1:6 in mole ratio) to a mixture of NaOH and hydrogen peroxide solution, coprecipitate was formed with rapid oxidation of ferrous to ferric ion. The coprecipitate transformed to single phase Co2Y powder at heat treatment temperatures as low as 900. The shape of Co2Y particles obtained at 900 was hexagonal plate-like (diameter∼, aspect ratio>10). The structure of the Co2Y was refined by a Rietveld analysis of the measured X-ray diffractogram. The lattice parameters are ao=5.8602 and co=43.512. Co2Y is a soft magnetic material with saturation magnetization 30 emu/g and coecivity 170 . A standard X-ray diffraction pattern for Co2Y is proposed as well.

Ti-B-C system ceramics composition were prepaed from the mixture of metal titanium, boron and graphite power by the self-propagating high-temperature synthesis method. The major crystalline phase as a function of boron content was TiC for mixture decreasing boron and TiB2 for these increasing boron. The combustion mode observed by a high-speed camera was steady-state. The combustion velocity increased with increasing the TiB2 product about TiC product. Ti:B:C as 2:2:1 specimen showed, Vicker's hardness of 2412kg/㎟ for 0.5 kg load, three-point flexure strength of 677 MPa and relative density of 98.3%

Crack free PbTiO3 ceramics were produced by sol-gel processing using alkoxide, which has not been reported to be successful. The PbTiO3 gels were prepared from Ti alkoxide and lead acetate without any dopants. They were calcined at and miled to produce fine PbTiO3 powder. It was pressed into discs and they were sintered at 110 for a few hours. The sintered ceramics were relativley hard and dense as having about 96% of theoretical density of PbTiO3. Fabrication of pure PbTiO3 ceramics by sol-gel processing is possibly due to their small grain size and uniform distribution of residual stress created during cubic-tetragonal transition over large number of small grains in fine grain PbTiO3 ceramics.

PLZT thin films were prepared using sol-gel spin coating. The films mainly consisted of perovskite phase when heat treated at 600 and in O2 or air atmosphere for 2 hours after 7 coating cycles. Cracks were formed when smaller than after 9 coating cycles. When ITO interlayer existed between Corning 7059 glass substrate and the film, cracks were not formed after 9 coating cycles, but cracks were formed after 11 coating cycles because of large volume change of the film contracting on the substrate during the heat treatment. In the observation of microstructure, the thin films have perovskite phase of about 2 grain size and pyrochlore phase of 100∼200 grain size.

CaO and ZnO were added to Al2O3-SiO2 binary system respectively as flux, then ZrO2 and TiO2 were applied as nucleating agent to these CaO-Al2O3-SiO2 and ZnO-Al2O3-SiO2 ternary system glass. The transparency could not be kept in CaO-Al2O3-SiO2 system glass, whereas the transparent glass-ceramics were prepared in ZnO-Al2O3-SiO2 system glass containing ZrO2 as the nucleating agent. At this time the optimum heating temperatures for the nucleation and the crystal growth were 78 and 97. The sizes of the precipitated crystals in the transparent glass-ceramics were below 0.1 , and their light transmissibilities were more than 80%.

Densification behavior, microstructural evolution, and mechanical properties of hot-pressed specimens using -SiC and -SiC powder with Al2O3 additive were studied. Beta-SiC powder was fully densified as 205, but -SiC powder was at 210. The maximum flexural strength and the fracture toughness of the specimen hot-pressed using -SiC powder were 681 MPa and 6.7 MPa{{{{ SQRT {m } }}, and thosevalues of specimen hot-pressed using -SiC powder were 452 MPa and 4.7 MPa{{{{ SQRT {m } }}, respectively. The strength superiority of specimen hot-pressed using -SiC powder was due to the finer grain size, and higher density. The higher toughness of specimen hot-pressed using -SiC powder than -SiC powder than -SiC powder was due to the crack deflection mechanism arised from the difference of thermal expansion coefficient between and -SiC phases which were co-existed in the sintered body.

The effects of slip composition and processing conditions on the fabrication of ceramic heat exchanger cores by doctor blade process were investigated. Since the effects of those two variables were inter-dependent, the effects of binder system, binder plus plasticizer, were extensively studied for a limited range of processing conditions and a pre-determined ceramic composition. The content of binder system and the ratio of binder to plasticizer were identified as main variables to affect densities and mechanical properties of green sheets, compressive properties and bond strengths of laminates, and shrinkages and their anisotropy of sintered laminates. However, sintered densities and water absorptions of laminates were not influenced by either the content of binder system or the ratio of binder to plasticizer, when the debinded laminates had a relatively high density (relative density of >55% in this study).