The effect of (Ni2+ + Sr2+) co-doping on structure and dielectric properties of Bi1.5MgNb1.5O7 pyrochlores

Abstract

The dielectric properties of bismuth-based cubic pyrochlore largely depend on the A-site cation. The effect of (Ni2+ + Sr2+) co-doping on the structure and dielectric properties of Bi1.5MgNb1.5O7 (BMN) was investigated. It reveals that the Ni2+ and Sr2+ in the co-doped Bi1.5Mg0.5NixSryNb1.5O7 (BNSN, x = 0.0–0.3 mol%, y = 0.0–0.2 mol%) ceramics preferentially replaced the Mg2+ on the A-site. For the samples with x = 0.3 and y < 0.2, it showed a very low dielectric loss (∼0.0003, 1 MHz). The dielectric loss of BNSN gradually increased with the increase of Sr2+ doping. However, the dielectric constant increased with increasing Sr2+ content. The BNSN exhibited a large dielectric constant (∼166, 1 MHz) at x < 0.3 and y = 0.2. Ni-doping would reduce the oxygen vacancy, which in turn decrease the dielectric loss. While, the increasing dielectric constant is attributed to the high ion polarizability of Sr2+ ions.