Antiferrodistortive phase transition in Pb(Ti0.48Zr0.52)O3:: A powder neutron diffraction study -: art. no. 060102

Results of a powder neutron diffraction study of the high-temperature monoclinic (F-M(HT)) to a low-temperature monoclinic (F-M(LT)) phase transition in Pb(Ti1-xZrx)O-3 discovered recently by Ragini et al. are presented for x = 0.520. The powder neutron diffraction pattern of the F-M(LT) phase contains superlattice reflections which have all odd hkl (hnot equalknot equall) Miller indices with respect to a doubled elementary perovskite cell, characteristic of antiphase tilting of oxygen octahedia. In analogy to other perovskite systems, the appearance of these superlattice reflections is attributed to an instability at the R point of the cubic Brillouin zone. We show that the most plausible space group of the F-M(LT) phase is Pc. Results of Rietveld refinement for this space group are presented to show that the oxygen octahedra indeed undergo antiphase rotations about [001] direction.