Diffuse phase transition in La and Ga doped barium titanate

Phase transitions in BaTiO3 and Ba1−xLaxTi1−xGaxO3 ( y = 0.008 , 0.012, 0.016 and 0.02) have been studied by high temperature X-ray diffraction (HTXRD) and Raman spectroscopy. All the compositions in these systems exhibit a single phase. The HTXRD and Raman spectra have been recorded between room temperature and 250 ∘C. The XRD data has been analyzed using the FULLPROF Rietveld refinement package. In compositions with higher diffuseness, the tetragonal phase exists well above the transition temperature ( T max ) observed in the dielectric constant vs temperature plot. Unlike pure BaTiO3 where T max is accompanied by a crystallographic transition, Ba1−xLaxTi1−xGaxO3 systems do not exhibit any crystallographic transitions at T max . The difference between the T max and crystallographic transition temperature is proportional to the extent of diffuseness of the transition.