Jing Feng
Kunming University of Science and Technology, Republic of China
Title: High temperature phase transformation and the mechanism in YTaO4
Biography
Biography: Jing Feng
Abstract
High temperature phase transformation and the mechanism in YTaO4 ceramics as potential thermal barrier coatings material is investigated by experiments and first principles calculation. High temperature in-situ XRD and Raman were indentified the phase transformation of yttrium tantalate. HRTEM showed the microstructure of phase transformation between monoclinic phase and tetragonal phase. The mechanism of phase transformation was discussed by the first principles canlualtion combined the Landau free energy expansion. Calculations of Gibbs free energies show that the phase transformation temperature at 1430 oC, close to the experimental value of 1426 +/- 7 oC. Landau free energy expansions demonstrate that the transition is second order and, based on the fitting to experimental and calculated lattice parameters, it is found that the transition is a proper rather than a pseudoproper type. Together these finding are consistent with the transition being ferroelastic.