Neutron Powder Diffraction Study of Pb(HfxTi1-x)O3 Ceramics (0.10 ≤ x ≤ 0.50)

摘要: The crystal symmetries of lead hafnate titanate (Pb(HfxTi1-x)O-3, PHT) powders with 0.10 <= x 0.50 were investigated by high-resolution neutron powder diffraction. Samples 0.40 tetragonal (space group P4mm), while the sample = contained both monoclinic Cm and rhombohedral (modeled using R3c space group) phases. role B cations (Hf Ti) oxygen octahedra network, in addition to displacement Pb ions from their ideal sites, promoting phase transformation between P4mm phases was considered. Two types structural disorder identified. Diffuse scattering Bragg reflection peaks assigned ion displacement. A second type disorder, revealed weak intensities observed pseudo-cubic 00/ reflections / even as 001 peak widths significantly broader than 100 peaks, observed. This behavior attributed arrangement O-B-O rows parallel c axis. For small values x, this shift predominantly along axis, whereas shifts perpendicular axis increased increasing x. These features modeled an hkl-dependent line-broadening model. origin W-dependent line broadening microstrain accompanying a spatial-composition variation. Structural models tested computing valence sums spontaneous polarization values.