Synthesis and Investigations of Ilmenite Structure Zn1-xAxTi1-yByO3

• Main Authors: Yee-Shin Chang, 張益新
• Other Authors: Yen- Hwei Chang
• Format: Others
• Language: zh-TW
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/z9w6x2

博士 === 國立成功大學 === 材料科學及工程學系碩博士班 === 92 === 　　The present investigation has been focused on the ZnTiO3, which has an ilmenite structure. The ZnTiO3 powders doped with Mg and Zr ions resulting (Zn,Mg)TiO3 and Zn(Ti,Zr)O3 multi-functional ceramics were synthesized. The experimentation consists of four parts, as ZnTiO3 powders preparation using sol-gel method, ZnTiO3 powders preparation by solid state reaction, synthesis and characterization of (Zn,Mg)TiO3 and synthesis and characterization of Zn(Ti,Zr)O3. 　　Experimental results show that the decomposition of the precursor proceeded through four major steps including dehydration reaction, decomposition, combustion reaction and ZnTiO3 phase formation. The ZnTiO3 phase was formed initially at 510℃and the optimum condition for ZnTiO3 powders is calcined at 800℃ for 10 h. The shape of grains will be changed from granular to fiber as the calcination temperature increasing from 800 to 1000℃. The activation energy of crystallization and grain growth for ZnTiO3 is ~ 160.50 kJ/mol and ~ 16.36 kJ/mol, respectively. 　　For solid state reaction, the crystallization temperature of ZnTiO3 powder was ~ 820℃, activation energy for crystallization was ~ 308.66 kJ/mol and ~ 23.94 kJ/mol for grain growth. In addition, ZnTiO3 is a V-type resistivity-temperature characteristics and possesses a typical PTCR properties above the Curie temperature (TC ~ 5℃). 　　For ZnTiO3 doped with MgO, the results revealed that Mg can replace the zinc ion and forms a solid solution in ZnTiO3 phase. The electrical resistivities of (Zn1-xMgx)TiO3 varied with sintering temperature, a minimum when sintered at 900℃ were obtained. Increasing amounts of Mg will also decrease the resistivity. A V-shaped temperature dependence of resistivity was observed. Furthermore, the dielectric constant increased with sintering temperature and decreased with increasing amounts of magnesium. It also shows a maximum Q factor (~1700) at a frequency of 8 GHz for the sample of (Zn0.9Mg0.1)TiO3 sintered at 900℃. For ZnTiO3 doped with ZrO2, the results indicated that the phase stable region of the hexagonal Zn(Ti1-xZrx)O3 extended to higher temperature. The surface morphologies, densities and dielectric properties exhibited a significant dependence on the sintering temperature and the amounts of additions. It reveals that higher amount of Zr addition favors to inhibit the grain growth of matrix. There are severely decreases in densities but increases in dielectric constants for Zr doped samples that sintered at the temperature higher than 900℃. The dielectric constant decreased and Curie temperature (Tc) increased slightly with increasing the amounts of Zr ions. Furthermore, the diffuse phase transition in Zn(Ti1-xZrx)O3 was observed.