Pressure-induced low symmetry phases in Ti-rich lead zirconate titanate PbZr0.20Ti0.80O3

The titanium-rich PZT solid solution PbZr0.20Ti0.80O3 was studied under high pressure by X-ray diffraction and Raman spectroscopy. A series of low-symmetry phases were observed, including monoclinic (space groups Cm and Cc) and triclinic forms (space groups F  1 and F1¯) in PbZr0.20Ti0.80O3. High pressure Raman spectra obtained are consistent with a monoclinic (Cc)–triclinic (F1) phase transition involving a soft mode at 9 GPa, in agreement with the change in compressibility detected by X-ray diffraction. The strong Raman spectra observed in the paraelectric phase can also be explained by the triclinic F1¯ symmetry.