Structure determination and microwave dielectric properties of La(MgSn)<inf>0.5</inf>O<inf>3</inf> ceramics

La(MgSn)0.5O3 (LMS) has been prepared by solid-state reaction method. A single perovskite phase with super lattice reflections corresponding to octahedral tilting, A-site cation displacement and 1:1 B-site ordering was observed in X-ray diffraction pattern. The Rietveld analysis was carried out with the initial model obtained from Structure Prediction and Diagnostics Software (SPuDS). The structure is determined to be monoclinic with space group P21/n corresponding to a-a-c+ tilting system. Long range ordering parameter (LRO) between Mg2+ and Sn4+ ions is calculated to be 89%. Dielectric characterization at microwave frequencies is also carried out. The dielectric constant (εr), product of quality factor and resonant frequency (Q.f) and temperature coefficient of resonant frequency (τf) of the sample sintered at 1600 °C are 20.1, 63,000 (GHz) and -78 (ppm/°C), respectively. © 2006 Elsevier Ltd. All rights reserved.