Broadband inelastic light scattering study on relaxor ferroelectric Pb(In_(1/2)Nb_(1/2))-Pb(Mg_(1/3)Nb_(2/3))O_3-PbTiO_3 single crystals

摘要

The broadband inelastic light scattering spectra of ternary Pb(In_(1/2)Nb_(1/2))-Pb(Mg_(1/3)Nb_(2/3))O_3-PbTiO_3 single crystals were investigated as a function of temperature and crystal orientation by combining Raman and Brillouin spectroscopies. The angular dependence of the strong Raman peak located at ～50 cm~(-1) was investigated at 300℃. The intensity variation of this mode with rotation angle was compatible with the F_(2g) mode of Fm3m symmetry, suggesting that this mode arises from the 1:1 chemical order at the B-site in this perovskite structure. The temperature evolution of the polar nanoregions was associated with the growth of two central peaks and the change in the intensity of some Raman peaks, which were known to be sensitive to the rhombohedral symmetry. Both relaxation processes exhibited partial slowing-down behaviors with a common critical temperature of ～160℃. Poling the crystal along the 001 direction induced abrupt changes in some of the Raman bands at the rhombohedral-tetragonal phase transition. On the other hand, the diffuse tetragonal-cubic phase transition was not affected by the poling process. This high-temperature phase transformation seems to be smeared out by the inherent disorder and strong random fields enhanced by the addition of Pb(In_(1/2)Nb_(1/2)) into Pb(Mg_(1/3)Nb_(2/3))O_3-PbTiO_3.