Vibrational studies of A(B′2/3B″1/3)O3perovskites (A = Ba, Sr; B′ = Y, Sm, Dy,Gd, In; B″ = Mo, W)

Abstract

The Raman- and IR-active phonons were studied in orderedBa(Y2/3Mo1/3)O3,Ba(Y2/3W1/3)O3,Ba(Gd2/3W1/3)O3,Ba(Sm2/3W1/3)O3,Ba(Dy2/3W1/3)O3,Ba(Dy2/3Mo1/3)O3 andBa(In2/3W1/3)O3 as well asdisordered Ba(In2/3Mo1/3)O3 and Sr(In2/3W1/3)O3. The assignment of the observed modes was given on the basis of lattice dynamical calculations. Thestudies performed revealed the presence of forbidden by the selection rules Raman bands for theBa(In2/3Mo1/3)O3 sample. This resultsuggests that the Ba(In2/3Mo1/3)O3 contains 1:1 ordered domains of symmetry embedded in the disordered matrix and that Ba(In2/3Mo1/3)O3 and Ba(In2/3W1/3)O3 may be obtained in both ordered and disordered structures, dependingon the thermal treatment. This behaviour resembles that of well knownPb(In1/2Nb1/2)O3,Pb(Sc1/2Nb1/2)O3 and Pb(Sc1/2Ta1/2)O3 relaxors.