Structure and properties of La(Zn1/2Ti1/2)O3

(La,Nd)(Zn,Mg)(0.5)Ti0.5O3 compounds are of great interest for microwave dielectric applications, although the structure of some of these complex perovskites is still uncertain. The perovskite tolerance factors in this family of compounds range from 0.916 to 0.952, suggesting a very high degree Of tilting in the oxygen octahedra for compositions throughout the system. The effects of this tilting in La(Zn0.5Ti0.5)O-3, for example, have been observed in this study by transmission electron microscopy in the form of 1/2{311}(c), and 1/2{131} alpha superlattice reflections and 1/2(231)(c) gamma reflections corresponding to anti-phase and in-phase tilting, respectively. Systematic La+3 displacement was also detected by the appearance of {h+1/2, k,l}(c) (beta) reflections. Reflections of the type 1/2{111}(c) in neutron diffraction patterns indicate 1: 1 cation ordering on the B-site. Electrical tests show no piezoelectricity in La(Zn0.5Ti0.5)O-3, indicating a centrosymmetric point group. Rietveld refinements of neutron diffraction patterns indicate that the space group is P2(1)/n, with lattice constants a = 7.8943 angstrom, b = 5.5959 angstrom, c = 5.5805 angstrom, and beta = 90.0291 degrees. (c) 2005 Elsevier Ltd. All rights reserved.