Raman study of the ordering in Sr(B0.5′Nb0.5)O3 compounds

Abstract

Strontium based complex perovskites are potential candidates for microwave integrated circuit applications. In the present article, we report on Raman scattering studies of cubic and noncubic structures of Sr(B0.5′Nb0.5)O3 [B′=Ga, In, Y, La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, and Yb] based complex-perovskite materials for an improved understanding of structure-property relations. The spectral results are compared to some tantalum analogues of known crystal structure. The present study reveals a higher degree of ordering for the tantalum compounds compared to those of the niobium analogues. Vibrational studies show a correlation between the tolerance factor and symmetry of these materials.

Temperature Raman scattering study of CaAl0.5Ta0.5O3 perovskite crystal

“…In this case the change in wavenumber obtained by authors was 37 cm -1 and 15 cm -1 for E g and A 1g mode, respectively. It is also known from the literature that such a substitution does not significantly influence the position of deformation F 2g mode [11,14,15].…”

Raman scattering study of (SrAl0.5Ta0.5O3)1‐x‐y: (LaAlO3)x : (CaAl0.5Ta0.5O3)y solid solution crystals

“…However, in AB' 1/2 B" 1/2 O 3 compounds the loss of translational and inverse symmetries due to disordering in the B sublattice will lead to the appearance of some bands in Raman spectrum [6,[8][9][10].…”

“…its intensity strongly decreases with the decrease of degree of order. The sharpness and intensity ratio of the F 2g (2)/A 1g vibrational modes can be a key factor for determining the degree of order in complex-perovskites [6]. The evolution of Raman spectra for set of samples starting from cubic 15 through tetragonal 2, 3, 4 to orthorhombic 6 are presented in Fig.…”

“…The A 1g mode is the breathing mode of the oxygen octahedra with Ta 5+ ion in its centre, while medium intense E g mode appears from asymmetric stretching vibrations of oxygen octahedra with Al 3+ ion in its centre. The F 2g (1) and F 2g (2) modes were assigned to external lattice vibration, predominantly caused by the motion of A ion and internal vibrations of an oxygen octahedron, respectively [6][7][8][9].…”

“…In SAT:LA compound (AB'1/2B"1/2O3), 1:1 order creates a cubic superstructure with Fm3m symmetry and lattice parameter a = 2a c (a c is the simple cubic axis) with two formula units in the primitive cell and ____________________ * Corresponding author: e-mail: tomrun@phys.put.poznan.pl regular alternation of B' and B" ions along all cubic axes [6]. The Raman studies of this compound and other crystals from AB'1/2B"1/2O3 family suggest arguments in favour of 1:1 order [7][8][9].…”