Enhancement of Giant Dielectric Response in Ba(Fe_0.5Nb_0.5)O₃ Ceramics by Al Substitution

Abstract

The structures and dielectric properties of Ba[(Fe_1-xAl_x)_0.5Nb_0.5]O₃ (x = 0, 0.1) ceramics were presented. Single-phase Ba[(Fe_1-xAl_x)_0.5Nb_0.5]O₃ (x = 0, 0.1) ceramics with a cubic crystal structure in space group (221) were obtained. Al substitution can significantly enhance the giant dielectric response, reduce the dielectric loss and improve the frequency and temperature stabilities of Ba(Fe_0.5Nb_0.5)O₃ ceramics. The giant dielectric constant step (25,000 at 10 kHz and 20,000 at 100 kHz) and the room-temperature dielectric loss (0.89 at 10 kHz and 6.58 at 100 kHz) are obtained in the Ba(Fe_0.5Nb_0.5)O₃ ceramics, while the giant dielectric constant step in the Ba[(Fe_0.9Al_0.1)_0.5Nb_0.5]O₃ ceramics is higher (36,000 at 10 kHz and 34,000 at 100 kHz) and the room-temperature dielectric loss is lower (0.15 at 10 kHz and 0.49 at100 kHz). XPS analysis results confirm that the dielectric relaxation originate from the mixed-valent structure of Fe²⁺/Fe³⁺ and the hopping of charge carriers between them, and the improvements of dielectric characteristics in Al-substituted Ba(Fe_0.5Nb_0.5)O₃ ceramics are attributed to the modification of such mixed-valent structure of Fe²⁺/Fe³⁺. These improvements of dielectric characteristics have great scientific significance for potential application of giant dielectric constant materials.

• Keywords Al substitution
• Ba(Fe_0.5Nb_0.5)O₃ ceramics
• the giant dielectric response
• mixed-valent structure

Funding

The present work was supported by National Science Foundation of China (51372144, 51102159, 51572160), the Special Foundation of Educational Department of Shaanxi Province (14JK1080), the Scientific Research Foundation for Ph.D (BJ10-16), the Academic Backbones Cultivation Program (XS11-02) and Graduate Innovation Fund of Shaanxi University of Science and Technology.