Structure and phase transitions in 0.5(Ba0.7Ca0.3TiO3)-0.5(BaZr0.2Ti0.8O3) from −100°C to 150°C

The solid solution of (x)Ba0.7Ca0.3TiO3-(1-x)BaZr0.2Ti0.8O3 is known to exhibit high piezoelectric constants. Discrepancies in the reported phase transitions and structure around room temperature, however, have complicated the understanding of the enhanced properties. Rietveld refinement of high-resolution X-ray diffraction is employed here to establish and refine the crystallographic structure at temperatures from -100 degrees C to 150 degrees C for x = 0.5. A combination of rhombohedral R3m and tetragonal P4mm is found to coexist at temperatures of 20 degrees C and -25 degrees C, bordered by single phase rhombohedral and tetragonal regions at lower (i.e., -100 degrees C) and higher (i.e., 70 degrees C) temperatures, respectively. The diffractograms also show signs of strain and domain wall scattering that are linked to the sample history. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4772741]