Polar order and diffuse scatter in Ba(Ti1-xZrx)O3 ceramics

The Ba(Ti1-xZrx)O-3 (BTZ) system with x < 0.35 has been studied using a combination of x-ray diffraction, dielectric measurements, Raman spectroscopy, and electron diffraction with a view to better understand the changes in structure and correlation length of polar order as a function of composition and temperature. Careful fitting of Raman spectra has confirmed stabilization of the orthorhombic phase at room temperature in x=0.05 with mixed phase (orthorhombic and rhombohedral) present at 80 K. Raman data suggest that the rhombohedral phase is most likely to be present at low temperature for x=0.15 and 0.25 and that only short range polar order evolves in x=0.35. Interpretation of the Raman spectra is in broad agreement with the dielectric data as a function of composition and temperature. Diffuse scatter at room temperature in high order zone axis electron diffraction remains essentially identical for all compositions irrespective of structure and correlation length of polar order. The diffuse maxima are therefore considered not to relate directly to the correlation length of polar order in the BTZ system and therefore do not contribute to the dielectric behavior.