Grain boundaries of CaCu₃Ti₄O₁₂ (CCTO) materials have been shown to play leading role in colossal permittivity. Core-shell design is an attractive approach to make colossal dielectric capacitors by controlling the grain boundaries. Core-shell grains of CCTO surrounded by Al₂O₃ shell were synthesized by ultrasonic sol-gel reaction from alumina alkoxide precursor. The influence of alumina shell by comparison with bare CCTO grains was studied. Particularly, microstructure, dielectric and electric effects on sintered ceramics are reported. The average grain size and the density are increased compared to undoped CCTO leading to an improvement of permittivity from 58,000 to 81,000 at 1 kHz. Furthermore a decrease of dielectric loss is found in a frequency range of 10²–10³ Hz. Moreover, the activation energy of grain boundaries is increased from 0.55 to 0.73 eV and the electrical properties such as breakdown voltage, non-linear coefficient and resistivity are improved with the aim of making industrial capacitors.

已显示CaCu ₃ Ti ₄ O ₁₂（CCTO）材料的晶界在巨大介电常数中起着主导作用。核壳设计是通过控制晶界来制造巨大介电电容器的一种有吸引力的方法。CCTO的芯壳晶粒被Al ₂ O ₃包围由铝醇盐的前驱体通过超声溶胶-凝胶反应合成壳。通过比较裸露的CCTO晶粒，研究了氧化铝壳的影响。特别地，报道了对烧结陶瓷的微观结构，介电和电效应。与未掺杂的CCTO相比，平均晶粒尺寸和密度增加，从而导致介电常数在1 kHz时从58,000提高到81,000。此外，在10 ² –10 ³  Hz的频率范围内发现介电损耗降低。此外，以制造工业电容器为目的，将晶界的活化能从0.55eV增加到0.73eV，并且改善了诸如击穿电压，非线性系数和电阻率的电性能。