RAMAN-STUDY OF THE RELATIONSHIP BETWEEN ROOM-TEMPERATURE TETRAGONALITY AND THE CURIE-POINT OF BARIUM-TITANATE

Variable-temperature Raman spectroscopy showed that, in progressively finer BaTiO3 powders, the Curie point increased as the room temperatur e tetragonality decreased. The influence of crystallite size distribut ion on the range of tetragonalities present in a powder was clearly ev ident in both phase transitions, as observed by Roman spectroscopy and room-temperature X-ray diffraction patterns, Titanium K-edge X-ray ab sorption spectroscopy could not distinguish between the cubic and tetr agonal structures of BaTiO3, at 300 degrees C and room temperature, re spectively.