Structure stability of multiferroic compound Bi2NiTiO6 under high pressure and temperature

Structural of multiferroics Bi2NiTiO6 under high pressure was studied in diamond-anvil cell (DAC) combined with synchrotron radiation X-ray diffraction. Crystal structure refinement shows that there are two isostructural phase transitions at $\sim $2 GPa and in the range of 15.5$\sim $18.5 GPa, respectively. The bulk modulus was derived from Birch-Murnaghan equation of state (EOS). Bi iron discontinuous movement is thought to be the source of all the isostructural phase transitions. Temperature dependence of X-ray diffractions were collected from room temperature up to 550 $^{\circ}$C. Structure refinement shows that an isostructural phase transition at temperature higher than 550 $^{\circ}$C can be compare with the isostructural phase transition in the range of 15.5$\sim $18.5 GPa.