在不同烧结温度下,利用传统的固相反应工艺制备了一系列NaCu3Ti3Sb0.5Ta0.5O12陶瓷,系统测试了它们的晶体结构、微观结构、介电性质和复阻抗谱.结果显示,所有的NaCu3Ti3Sb0.5Ta0.5O12陶瓷的主相都呈现类钙钛矿结构,介电性质随烧结温度变化很大.高于1020℃烧结的陶瓷的室温相对介电常数大于3000,具有高介电性质.复阻抗谱显示,NaCu3Ti3Sb0.5Ta0.5O12陶瓷的电学分布不均匀,由绝缘性的晶界和半导性的晶界组成.通过XRD和XPS测试发现,在陶瓷中观察到了CuO第二相和Cu、Ti、Sb、Ta离子的变价.因此,利用内阻挡层电容效应可以解释NaCu3Ti3Sb0.5Ta0.5O12陶瓷的高介电性质.
A series of NaCu3Ti3Sb0.5Ta0.5O12ceramics were prepared by conventional solid-state reaction technique at different sintering temperatures. Their crystalline structures, microstructures, dielectric properties and complex im-pedance were systematically investigated. All the ceramics show the main phase of perovskite-related crystallographic structure, and their dielectric properties change significantly with sintering temperature. Those ceramics sintered above 1020℃ perform high dielectric-permittivity properties with ε' over 3000. Impedance spectroscopy analysis reveals that NaCu3Ti3Sb0.5Ta0.5O12ceramics are electrically heterogeneous and composed of semiconducting grains and insulating grain boundaries. Moreover, a small amount of CuO secondary phase and Cu2+/Cu+, Ti4+/Ti3+, Sb5+/Sb3+and Ta5+/Ta3+aliovalences are found to exist in NaCu3Ti3Sb0.5Ta0.5O12ceramics through XRD and XPS analysis. Internal barrier layer capacitance effect suggests the origin of the high dielectric-permittivity properties in NaCu3Ti3Sb0.5Ta0.5O12ceramics.