Potential Functions of Ions in Cubic BaTiO3

Abstract

Integrated intensities of X-ray Bragg reflections (Ag-K α radiation) from barium titanate single crystal were measured as a function of temperature above the Curie point of 131.2°C. The harmonic and fourth order anharmonic potential parameters for constituent ions were estimated from the thermal vibration amplitude of each ion. Potential parameters are: α(Ba)=1.018 ×10 -11 erg A -2 , α(Ti)=0.730 ×10 -11 erg A -2 , α(O)=0.265 ×10 -11 erg A -2 , α'(O)=0.999 ×10 -11 erg A -2 , γ(Ba)=0.055 ×10 -11 erg A -4 , γ(Ti)=0.679 ×10 -11 erg A -4 , γ(O)=-0.400 ×10 -11 erg A -4 , γ'(O)=2.99 ×10 -11 erg A -4 ; and the Gruneisen constant is 1.22. These values are consistent with suggestions presented in previous neutron diffraction studies by Y. Yamada et al. and J. Harada et al.