Crystal Structure of Dielectric Ceramics in the La(Mg_0.5Ti_0.5)O₃–BaTiO₃ System

The crystal structure of microwave dielectric ceramics in the (1 − x)La(Mg_0.5Ti_0.5)O₃ (LMT)–xBaTiO₃ (BT) (0 ≤ x ≤ 0.9) system has been refined by Rietveld method using x-ray powder diffraction data. LMT and BT were found to form a solid solution in the whole compositional range. The increase of BaTiO₃ content results in the following sequence of structure transformations of those solid solutions: P2₁/n (a⁻a⁻c⁺, B-site ordered) → Pbnm (a⁻a⁻c⁺) → I4/mcm (a⁰a⁰c⁻) → Pm3m (a⁰a⁰a⁰). These structural changes are related to the disappearance of B-site cation ordering (x > 0.1), in-phase tilting (x > 0.3), and antiphase tilting (x > 0.5), respectively.