Extremely low dielectric loss of Mg and Al co-substituted CCTO ceramic with excellent temperature stability
Achieving both low dielectric loss (tan δ ) and high temperature stability of ceramic capacitors can greatly broaden their potential application. In this study, the effects of Mg and Al co-substitution on the microstructure and dielectric properties of CCTO-based ceramics were investigated in CaCu 3- x Mg x Ti 4- x Al x O 12 ( x = 0, 0.025, 0.050, and 0.075) ceramics prepared by a sol-gel method. XRD analysis shows that the primary crystalline phase of CCTO is formed in all samples, indicating that Mg 2 + and Al 3+ have entered the lattice. SEM results reveal the co-substitution of Mg and Al inhibits the grain growth, leading to an increase in grain boundary density. All co-substituted samples exhibited low tan δ and excellent temperature stability. Notably, CaCu 2.95 Mg 0.05 Ti 3.95 Al 0.05 O 12 ceramics exhibited an extremely low tan δ of 0.007 (at 10 3 Hz) and its dielectric constant maintained excellent stability over a broad temperature spectrum (−125 to 150 °C), meeting the commercial standards for X8P capacitors. The reduction of tan δ is mainly attributed to the inhibition of grain growth in Mg and Al co-substituted samples, which increases grain boundary density and subsequently suppresses the mobility of oxygen vacancies, leading to an increase in grain boundary resistance. Furthermore, the improvement in temperature stability is ascribed to the reduction in the content of oxygen vacancies and the suppression of electron transitions between Ti 4+ and Ti 3+ as well as Cu 2+ and Cu + in Mg and Al co-substituted samples, resulting in an increase in grain boundary activation energy. These novel findings are hoping to contribute to not only the fabrication of new CCTO-based ceramics with extremely low tanδ and excellent temperature stability but also the application of CCTO-based ceramics at a very broad temperature range in electronic devices, new energy vehicles, aerospace, and polar scientific research equipment.
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