Origins of dielectric relaxations in AgNb7O18 ceramic

• Published in: Ceramics international Vol. 46; no. 14; pp. 23021 - 23026
• Main Authors: Qian, Yinjie, Wang, Jian, Asif, Sana Ullah, Xie, Jiyang, Hu, Wanbiao
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.10.2020
• Subjects: Bond valence energy landscape; Equivalent circuit modeling; Local chemical environment; Relaxor ferroelectrics; Equivalent circuit modeling; Local chemical environment; Bond valence energy landscape; Relaxor ferroelectrics
• ISSN: 0272-8842; 1873-3956
• DOI: 10.1016/j.ceramint.2020.06.078

The origins of the relaxor behavior and low-temperature dielectric relaxation processes in AgNb7O18 ceramic were studied and a new relaxation mechanism was proposed through combined bond valence energy landscape (BVEL) calculation and equivalent circuit modeling (ECM). The BVEL calculation suggests that the Ag1 displacement subjects to a double-well potential that originates from the anisotropic coordination symmetry and low coordination number at Ag1 site. The relaxor ferroelectric behavior, observed at 200 K ≤ T ≤ 270 K, is sensitive to thermal history and is ascribed to the Ag1 hopping in double-well potential. The temperature dependence of the matrix capacitance (obtained by ECM) is very similar with that of b axis (obtained by in situ XRD) at 123 K < T < 174 K. Therefore, a phase transition being responsible for the low-temperature dielectric relaxation is assumed. The combined BVEL and ECM techniques performed in this work are therefore quite helpful to understand the complicated relaxor phenomena and explore new relaxors.