The Effect of Cation Disorder on Ferroelectric Properties of SrxBa1-xNb₂O₆ Tungsten Bronzes

Solveig S Aamlid; Sverre M Selbach; Tor Grande

doi:10.3390/ma12071156

The Effect of Cation Disorder on Ferroelectric Properties of Sr_xBa_1-xNb₂O₆ Tungsten Bronzes

Materials (Basel). 2019 Apr 10;12(7):1156. doi: 10.3390/ma12071156.

Authors

Solveig S Aamlid¹, Sverre M Selbach², Tor Grande³

Affiliations

¹ Department of Materials Science and Engineering, NTNU Norwegian University of Science and Technology, NO-7491 Trondheim, Norway. solveig.s.aamlid@ntnu.no.
² Department of Materials Science and Engineering, NTNU Norwegian University of Science and Technology, NO-7491 Trondheim, Norway. selbach@ntnu.no.
³ Department of Materials Science and Engineering, NTNU Norwegian University of Science and Technology, NO-7491 Trondheim, Norway. grande@ntnu.no.

Abstract

The versatile crystal structure of tetragonal tungsten bronzes (A1₂A2₄C₄B₁₀O₃₀) can accommodate complex stoichiometries including cations in different valence states and vacant cation sites. Here, we report on the effect of thermally induced cation-vacancy disorder in the tetragonal tungsten bronze Sr_xBa_1-xNb₂O₆ (SBNX). SBNX (x = 0.25, 0.33, 0.50, 0.61) ceramics, prepared by conventional solid-state synthesis, were annealed at varying temperatures and subsequently quenched to room temperature. The Curie temperature of all the SBNX materials increased with higher quenching temperatures, accompanied with ferroelectric hardening. The variation in thermal history also caused structural changes, specifically a contraction of the a lattice parameter and a minor elongation of the c parameter. These effects are discussed in relation to recent first principles calculations of the energy landscape of the cation-vacancy configurations and experimental evidence of thermally induced cation-vacancy disordering.

Keywords: SBN; TTB; cation disorder; ferroelectricity; strontium barium niobate; thermal history; tungsten bronze.