Mg2MTaO6 (M = Nd or La):: a group of new pyrochlore oxides

Preparation of two novel mixed metal oxide ceramic materials, namely magnesium neodymium tantalum oxide (Mg2NdTaO6) and magnesium lanthanum tantalum oxide (Mg2LaTaO6) by conventional solid-state reaction method is reported in this paper. The crystal structure of these new compounds, were studied by indexing the X-ray diffraction patterns, powder pattern calculation and profile fitting. They were found to have a defective cubic pyrochlore structure, with the A site being randomly occupied by Mg and La/Nd, while, Ta and Mg are randomly distributed at the B site. The formula assigned were (MgNd)(MgTa)O-6 and (MgLa)(MgTa)O-6. The variation of dielectric constant, dielectric loss and conductivity of sintered pellets of these materials with applied frequencies in the range of 30 Hz-1 MHz were studied at room temperature. These room temperature studies at I MHz gave dielectric constant values of 24.8 and 25.35; conductivity values of 7.75 x 10(-6) and 8.27 x 10(-6) S/m as well as dielectric loss values of 0.0055 and 0.006 for Mg2NdTaO6 and Mg2LaTaO6, respectively. These new pyrochlore compounds were found to have dielectric constant, dielectric loss and conductivity values in the range suitable for possible electronic ceramic applications. (C) 2004 Elsevier Inc. All rights reserved.