粉体合成方法对CaCu3Ti4O12陶瓷介电性能的影响
Effects of Powder Synthesis Method on Dielectric Properties of CaCu3Ti4O12 Ceramics

为了深入研究粉体合成方法对CaCu3Ti4O12(CCTO)陶瓷介电松弛机理以及缺陷结构的影响,对比了固相反应法和溶胶凝胶法合成CCTO陶瓷的介电性能,并且在此基础上引入了CCTO陶瓷的缺陷结构分析。采用固相反应法和溶胶凝胶法合成了CCTO粉体,在1 080℃下烧结4 h制备了CCTO陶瓷样品。溶胶凝胶法合成陶瓷的平均晶粒尺寸是固相法合成陶瓷试样的5倍。J？？E特性和介电性能分析表明,溶胶凝胶法合成陶瓷的击穿场强(170 V/cm)远小于固相法合成陶瓷(4 980 V/cm),且前者的介电损耗和介电常数均达到后者的20倍左右。结合介电损耗因子的曲线拟合结果和阻抗谱分析得到,溶胶凝胶法合成陶瓷的晶界电阻为0.272 MΩ,是固相法(1.03 MΩ)的1/3,松弛峰强度是固相法的15倍;两种陶瓷样品的本征松弛峰活化能和晶粒活化能均接近,说明粉体合成方法能够影响CCTO陶瓷的晶界电阻和松弛峰强度,进而影响其宏观电性能,但是对陶瓷的本征松弛机理没有影响。
To investigate the effects of powder synthesis methods on dielectric relaxation mechanism and defect structure of CaCu3Ti4O12(CCTO) ceramics, two kinds of CCTO ceramics were synthesized. CCTO powders were obtained by solid？？state process and sol？？gel process. CCTO ceramic samples were prepared by corresponding CCTO powders and sintered at 1 080℃ for 4 hours. The obtained sol？？gel ceramic samples with average grain size 4 times larger than that of solid？？state sample presented an abnormal grain growth. The breakdown field was decreased from 4 980 V/cm for solid？？state sample to 170 V/cm for sol？？gel sample. Besides, the dielectric loss and dielectric constant of the latter are both 19 times higher. It is revealed by the impendence spectroscopy and ε″ curve fitting results that the grain boundary resistance of sol？？gel sample (0？？272 MΩ) is one third of that of solid？？state sample (1.03 MΩ), and the relaxation peak height of the former is about 14 times higher. However, the activation energies of intrinsic relaxation peaks are close for the samples from different synthesis processes. It is concluded that sol？？gel process leads to much lower grain boundary resistance and higher relaxation peak height, but exerts little effect on intrinsic dielectric relaxation mechanism of CCTO ceramics