Pressure induced phase transition of PbNiO3 from LiNbO3-type to perovskite

The phase transition of PbNiO3 from LiNbO3 structure to the perovskite structure has been observed between 4.4 and 9.5GPa, which was investigated by high-pressure synchrotron x-ray powder diffraction at room temperature. Compression behavior of the two phases has been analyzed, and the c axis is the soft direction for LiNbO3-type PbNiO3. The bulk modulus of the LiNbO3-type PbNiO3 is K0=184(3)GPa, K0′=4.5(9), and the perovskite type is K0=166(8)GPa, K0′=4.9(8).