Synthesis and characterisation of La0.4Ba0.6Ti0.6RE0.4 (where RE = Y, Yb) ceramics

La0.4Ba0.6Ti0.6RE0.4O3 (where RE = Y, Yb) powders were synthesised by the mixed oxide route. According to laboratory X-ray diffractometry both compositions are single-phase and can be indexed on the Pm (3) over barm. space group; however, electron diffraction suggests the occurrence of anti-phase octahedral tilting or 1: 1 ordering. Ceramics fired at 1600 degrees C for 4 h exhibit an average grain size of similar to 20 mu m. Bright field TEM images suggest the occurrence of chemical inhomogeneity in both compositions. The dc conductivities and Raman spectra are similar for both compositions; however, La0.4Ba0.6Ti0.6Y0.4O3 ceramics exhibit epsilon(r) similar to 57, quality factor (Qf) similar to 750 GHz and temperature coefficient of resonance (TCF) similar to 12 ppm/K, whereas La0.4Ba0.6Ti0.6Yb0.4O3 ceramics exhibit epsilon(r) similar to 65, Qf similar to 4500 GHz and TCF similar to 1 ppm/K. (c) 2005 Elsevier Ltd. All rights reserved