Abstract
In this work, two methods of CaCu3Ti4O12-CuAl2O4 composite and SrCu3Ti4O12-CaCu3Ti4O12 composite were prepared to improve the breakdown field in CaCu3Ti4O12 ceramics. CaCu3Ti4O12-0.5CuAl2O4 and 0.4SrCu3Ti4O12-0.6CaCu3Ti4O12 samples with proper sintering conditions were found to have greatly enhanced breakdown fields of more than 20 kV·cm−1 compared to the ordinary value of 1–2 kV·cm−1 in CaCu3Ti4O12 ceramics. In addition, reduced dielectric loss tangent of these samples remained about 0.1 at a low frequency of 0.1 Hz, indicating superior dielectric properties. No abnormal grain growth was found in either composite with a high breakdown field, which was attributed to the pining effect and consumption of Cu-rich phase at grain boundaries. Under analysis of the relaxation process by electric modulus, compared to conventional CaCu3Ti4O12 ceramics, interstitial Ali··· and increasing interfaces were responsible for variation in activation energy in CaCu3Ti4O12-0.5CuAl2O4 composites, while the integrated action of a strong solid solution effect and weak Sr-stretching effect contributed to the elevated potential barrier height and enhanced breakdown field in 0.4SrCu3Ti4O12-0.6CaCu3Ti4O12 composites.
Highlights
CaCu3 Ti4 O12 (CCTO) ceramics has been extensively studied due to its colossal dielectric constant (CDC) up to 105, which is frequency independent in 102 –106 Hz and exhibits excellent temperature stability over 100–600 K [1]
In the single-phase CCTO ceramics, Peak 2 is derived from the intrinsic defect closely related in solid solution, the generation of oxygen vacancy is difficult to achieve, increasing the intrinsic to the oxygen vacancy, corresponding to the deep trap energy level in the depletion layer
CaCu3 Ti4 O12 -0.5CuAl2 O4 composites prepared by an in-situ method and
Summary
CaCu3 Ti4 O12 (CCTO) ceramics has been extensively studied due to its colossal dielectric constant (CDC) up to 105 , which is frequency independent in 102 –106 Hz and exhibits excellent temperature stability over 100–600 K [1]. In addition to CDC, non-ohmic characteristic has been found in CCTO ceramics [2], which is promising in applications of energy storage capacitors and over-voltage protection devices Both the CDC property and non-ohmic characteristics are associated with defect-related double Schottky barrier between the semiconducting grains and insulating grain boundaries [3,4,5]. The breakdown voltage of CCTO could be enhanced to 13 kV·cm−1 with a dielectric constant of more than 1000 by direct introduction of secondary CuAl2 O4 phase [16]. Based on the analysis of the dielectric relaxation process, the reasons for the enhanced breakdown fields are discussed related to the potential barrier at the grain boundary
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