Conductivity, Dielectric Loss, and Electrical Heterogeneous Microstructure of Eight‐Layer Twinned Hexagonal Perovskite Ceramics Ba8CuTa6O24−δ. Issue 8 (19th April 2013)

• Record Type: Journal Article
• Authors: Yu, Xiaodi; Chai, Shiqiang; Kuang, Xiaojun; Su, Congxue; Pan, Fengjuan; Fang, Liang; Su, Qiang; Davies, P. K.
• Is Part Of: Journal of the American Ceramic Society. Volume 96:Issue 8(2013)
• Page Start: 2510
• Page End: 2514
• Publication Date: 2013-04-19
• Subjects: Ceramics -- Periodicals; 620.1405
• DOI: 10.1111/jace.12349
• Languages: English
• ISSNs: 0002-7820

Abstract

<abstract abstract-type="main" xml:lang="en" id="jace12349-abs-0001"> <title> <x xml:space="preserve">Abstract</x> </title> <p>Ba<sub>8</sub>CuTa<sub>6</sub>O<sub>24−δ</sub> ceramics possess exceptionally high microwave dielectric loss among the eight‐layer twinned hexagonal perovskite Ba<sub>8</sub>MTa<sub>6</sub>O<sub>24</sub> (M = Zn, Co, Ni, Mg, Cu) analogs. Impedance spectroscopy measurement demonstrates that the eight‐layer Ba<sub>8</sub>CuTa<sub>6</sub>O<sub>24−δ</sub> 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<sub>8</sub>CuTa<sub>6</sub>O<sub>24−δ</sub> ceramics. The heterogeneous electrical microstructure is associated with partial reduction of Cu<sup>2+</sup> to Cu<sup>+</sup> and oxygen loss during the sintering procedure and limited reoxidization along grain boundary regions on cooling. The existence of Cu<sup>+</sup> in Ba<sub>8</sub>CuTa<sub>6</sub>O<sub>24−δ</sub> ceramic is confirmed by X‐ray photoelectron spectroscopy measurement. The leaky insulating bulk property for the Ba<sub>8</sub>CuTa<sub>6</sub>O<sub>24−δ</sub> ceramics is compared with the highly insulating bulk behavior of other low dielectric loss analogs, which indicates that the significant defects of Cu<sup>+</sup> and oxygen vacancies are responsible for the high microwave dielectric loss of the Ba<sub>8</sub>CuTa<sub>6</sub>O<sub>24−δ</sub> ceramics.</p> </abstract>