High-Pressure Effect on ${\mathrm{PbTiO}}_3$: An Investigation by Raman and X-Ray Scattering up to 63 GPa

We report a room-temperature high-pressure x-ray and Raman scattering investigation of lead titanate (${\mathrm{PbTiO}}_3$) up to 63 GPa. Three continuous phase transitions at 13, 20, and 45 GPa between tetragonal-like phases occur. As a result, no evidence is found for a pressure-induced morphotropic phase boundary. Our study provides experimental evidence that ${\mathrm{PbTiO}}_3$ presents a complex sequence of phases accommodating pressure through mechanisms involving oxygen octahedra tilting and reentrance of ferroelectricity.

Figure 1

Pressure evolution of the lattice parameters of ${\mathrm{PbTiO}}_3$ from 0.1 to 63 GPa and of the $⟨004⟩$ Bragg spot (inset).

Figure 2

Rietveld refinement ($I4cm$) of a powder diffraction pattern obtained at 50 GPa. Insets: blowup of the (a) (111) and (b) (200) pseudocubic Bragg peak.

Figure 3

Selected Raman spectra of ${\mathrm{PbTiO}}_3$ as a function of pressure up to 44 GPa. Symmetry attribution according to Ref. 17.

Figure 4

Pressure dependence of PTO low wave number phonons up to 44 GPa. The solid lines represent the dependence expected for the uncoupled excitations $A_1$ and $2TA$. Typical Landau dependence of $A_1$ wave number is obtained with $p_c\simeq 13\mathrm{GPa}$ and an exponent of $1/2$.