A monoclinic ferroelectric phase in the Pb(Zr1−xTix)O3 solid solution

A previously unreported ferroelectric phase has been discovered in a highly homogeneous sample of ${\mathrm{PbZr}}_{\mathrm{0.52}}{\mathrm{Ti}}_{\mathrm{0.48}}{\mathrm{O}}_{\mathrm{3}}$ by high-resolution synchrotron x-ray powder diffraction measurements. At ambient temperature the sample has tetragonal symmetry ${\mathrm{(a}}_t\text{=4.037\hspace{0.05em}Å,}$ $c_t\text{=4.138\hspace{0.05em}Å),}$ and transforms below ∼250 K into a phase which, unexpectedly, has monoclinic symmetry ${\mathrm{(a}}_m\text{=5.717\hspace{0.05em}Å,}$ $b_m\text{=5.703\hspace{0.05em}Å,}$ $c_m\text{=4.143\hspace{0.05em}Å,}$ $\text{β=90.53°,}$ at 20 K). The intensity data strongly indicate that the polar axis lies in the monoclinic ac plane close to the pseudocubic [111] direction, which would be an example of the species $\text{m3m(12)A2Fm}$ predicted on symmetry grounds by Shuvalov.