Cation ordering in complex oxides

Abstract

Abstract.Several recent papers have addressed the fundamental aspects of the stability and kinetics of ordering in complex oxides, and investigated systems where the properties are mediated by the degree of order. Cation ordering reactions have been shown to induce large alterations in the dielectric, ferroelectric, magnetic, and electronic response of many complex oxides. The majority of the cited publications focus on ion ordering in perovskite related structures; however, additional examples include the ordering of structural slabs and formation of modulated intergrowth structures.Introduction.

Complex Polymorphic Behavior and Dielectric Properties of Perovskite-Related Sr(Sr1/3Nb2/3)O3

“…Additionally, non-stoichiometric A(B >V B \V )O \B perovskites exhibit ionic conductivity (4) and can also absorb signi"cant proton concentrations to become proton conductors (5,6). The typical crystal}chemical e!ects observed in these systems include B-cation ordering (7) and/or structural distortion approximated by rotation of nearly rigid [BO ] octahedra (8,9); both e!ects are known to substantially in#uence dielectric and electrical properties (8,10). For the stoichiometry A(B B )O , two common B-site ordering types have been reported with the ordering vectors k"1/3[111]* (1:2 type) and k"1/2[111]* (1:1 or NaCl type), respectively (7), where subscript &c' refers to the ideal cubic &4 A s perovskite unit cell.…”

Structural transitions in Pb(In1∕2Nb1∕2)O3 under pressure

“…On the other hand, quenched PIN crystal shows disordering on the B-site with broad frequency dispersive dielectric permittivity. 16 Here we studied the disordered PIN samples and observed that the sequence of pressureinduced transitions in disordered PIN crystal are rather similar to that of PbZrO 3 . 42 The first transition occurs in disordered PIN at around 0.5 GPa, we observe strong diffuse scattering even at 1.2 GPa (Fig.…”

“…Recent theoretical calculations and experiments point out that the displacement of Pb cation in these materials have strong correlations along particular crystallographic directions, that gives diffuse scattering in relaxor materials. 37,49 A common feature of high-pressure phase of Pb-based relaxors is a new peak appearing around 380 cm À1 in Raman spectra for all these studied Pb-based relaxor samples including PbTiO 3 . A similar peak appeared in PIN above 1 GPa, and the frequency of this peak is located around the bending mode region in general.…”

“…where K 0 is bulk modulus and K 0 0 is its pressure derivative, is applied to fit the pressure dependence of unit cell volume, which yields a bulk modulus of 99 (AE 16) GPa, its pressure derivative of 8 (AE 2), and an initial volume of 560 (AE 3) Å 3 below 33 GPa; a separated fit to the data above 33 GPa yields a bulk modulus of 316 (AE 20) GPa, its pressure derivative of 4 (fixed), and an initial volume of 521 (AE 15) Å 3 . Figure 8 shows a structure model (orthorhombic Pbam) constructed from the parameters obtained from a Rietveld fitting at 3.9 GPa.…”

“…1,2 The exceptional electromechanical properties of these Pb-based materials have generated intense interest in both scientific and industrial communities. While extensive theoretical and experimental studies have advanced our understanding of relaxor ferroelectrics, [3][4][5][6][7][8][9] their properties are still poorly understood. These difficulties stem from the complexity of these materials, which have a high degree of compositional, structural, and polar disorder.…”