Sintering and microwave dielectric properties of Zn2-2xSil+xO4 (x=O-0.10) ceramics were investigated. The secondary phase of ZnO was observed in the specimen for x=O whereas SiO2 was detected in that for x=0.05. The composition of Zn2SiO4 might be close to x=0.02, i.e., Zn1.96Si1.02O4; the ratio of Zn/Si is 1.922. The insufficient grain growth was observed in the specimen of x=O. For the specimens of x≥0.05 , the grain growth sufficiently occurred through the liquid phase sintering. The value of quality factor of all specimens was dependent on the x value, i.e., the ratio of Zn/Si, whereas that of dielectric constant was independent. Relative density, dielectric constant, and quality factor (Q×f) of the specimen for x=0.05, i.e., Znl.9Si1.05O4, sintered at 1,400℃ were 96.5%, 6.43, and 115,166 GHz, respectively.
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MICROSTRUCTURE, PHASE EVOLUTION, AND MICROWAVE DIELECTRIC PROPERTIES OF Li₂O AND Ga₂O ₃ DOPED ZINC ORTHOSILICATE Shin Kim Ceramics - Silikaty.2017; : 209. CrossRef
La7.33Bi2 (SiO4)6O2 specimens were fabricated by standard solid-state synthesis route for solid oxide electrolytes. The calcined powders exhibited uniform particles with a mean particle size of about 28μm. The room-temperature structure of La7.33Bi2 (SiO4)6O2 specimens was analyzed as hexagonal, space group P63 or P63/m, and the unit cell volume increased with increase a sintering temperature. The specimens sintered at 1,175℃ showed X-ray patterns of homogeneous apatite single phase without the second phase such as La2Si2O7 and La2SiO5. The specimen sintered at 1,175℃ showed the maximum sintered density of 5.49 g/cm3. Increasing the sintering temperature, total conductivities increased, activation energy decreased and the values were 1.98 × 10-5 Scm-1 and 1.23eV, respectively.
Synthesis of Li2MnSiO4 was attempted by the conventional solid-state reaction method, and the phase formation behavior according to the change of the calcination condition was investigated. When the mixture of the three source materials, Li2O, MnO and SiO2 powders, were used for calcination in air, it was difficult to develop the Li2MnSiO4 phase because the oxidation number of Mn2+ could not be maintained. Therefore, two-step calcination was applied: Li2SiO3 was made from Li2O and SiO2 at the first step, and Li2MnSiO4 was synthesized from Li2SiO3 and MnO at the second step. It was easy to make Li2SiO3 from Li2O and SiO2. Li2MnSiO4 single phase was developed by the calcination at 900℃ for 24 hr in Ar atmosphere as the oxidation of Mn2+ was prevented. However, the Li2MnSiO4 was γ -Li2MnSiO4, one of the polymorph of Li2MnSiO4, which could not be used as the cathode materials in Li-ion batteries. By applying the additional low temperature annealing at 400℃, the single phase β -Li2MnSiO4 powder was synthesized successfully through the phase transition from γ to β phase.
A Study of The Surface Dielectric Barrier Discharge Design Conditions for Generating Negative Air Ions Sang-Moon Shin, Jung-Yoon Kim, Jong-Soo Kim, Jae-Ha Choi, Won-Ho Choi Journal of the Korean Institute of Illuminating and Electrical Installation Engineers.2014; 28(1): 114. CrossRef
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