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 PbZr0.52Ti0.48O3 by high-resolution synchrotron x-ray powder diffraction measurements. At ambient temperature the sample has tetragonal symmetry (a(t) = 4.037 Angstrom, c(t) = 4.138 Angstrom), and transforms below similar to 250 K into a phase which, unexpectedly, has monoclinic symmetry (a(m) = 5.717 Angstrom, b(m) = 5.703 Angstrom, c(m) = 4.143 Angstrom, beta = 90.53 degrees, 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 m3m(12)A2Fm predicted on symmetry grounds by Shuvalov. (C) 1999 American Institute of Physics. [S0003-6951(99)00714-7].