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Conductivity, Dielectric Loss, and Electrical Heterogeneous Microstructure of Eight‐Layer Twinned Hexagonal Perovskite Ceramics Ba 8 CuTa 6 O 24−δ

2013; Wiley; Volume: 96; Issue: 8 Linguagem: Inglês

10.1111/jace.12349

1551-2916

Xiaodi Yu, Shiqiang Chai, Xiaojun Kuang, Congxue Su, Fengjuan Pan, Liang Fang, Qiang Su,

Ferroelectric and Piezoelectric Materials

Ba 8 CuTa 6 O 24−δ ceramics possess exceptionally high microwave dielectric loss among the eight‐layer twinned hexagonal perovskite Ba 8 MTa 6 O 24 (M = Zn, Co, Ni, Mg, Cu) analogs. Impedance spectroscopy measurement demonstrates that the eight‐layer Ba 8 CuTa 6 O 24−δ ceramics show the electrical heterogeneous microstructure, consisting of leaky insulating grains and more resistive grain boundary regions. This induced internal barrier layer capacitance (IBLC) effects on Ba 8 CuTa 6 O 24−δ ceramics. The heterogeneous electrical microstructure is associated with partial reduction of Cu 2+ to Cu + and oxygen loss during the sintering procedure and limited reoxidization along grain boundary regions on cooling. The existence of Cu + in Ba 8 CuTa 6 O 24−δ ceramic is confirmed by X‐ray photoelectron spectroscopy measurement. The leaky insulating bulk property for the Ba 8 CuTa 6 O 24−δ ceramics is compared with the highly insulating bulk behavior of other low dielectric loss analogs, which indicates that the significant defects of Cu + and oxygen vacancies are responsible for the high microwave dielectric loss of the Ba 8 CuTa 6 O 24−δ ceramics.