Effect of substitution of Nd~(3+) for Bi~(3+) on the dielectric properties and structures of SrBi_(2-χ)Nd_χNb_2O_9 bismuth layer-structured ceramics

摘要

Single phases of SrBi_(2-χ)Nd_χNb_2O_9 (χ =0, 0.1, 0.2, and 0.4) ceramics were prepared by the solid-state reaction method and studied by dielectric and Raman spectroscopy. The substitution of Nd~(3+) for Bi~(3+) induced a dielectric relaxation behavior for SrBi_(2-χ)Nd_χNb_2O_9 (χ=0.1, 0.2, and 0.4). When χ=0.4, the dielectric response of SrBi_(1.6)Nd_(0.4)Nb_2O_9 is characteristic of typical relaxor ferroelectrics, which could be attributed to the disorder induced by the Nd~(3+) substituting for Bi~(3+) in Bi_2O_2 layers. The dielectric relaxation of SrBi_(1.6)Nd_(0.4)Nb_2O_9 was fitted using the Voegel-Fulcher relationship, which indicates that SrBi_(1.6)Nd_(0.4)Nb_2O_9 is analogous to a spin glass with thermally activated polarization fluctuations above a static freezing temperature. Raman spectra of SrBi_(2-χ)Nd_χNb_2O_9 ceramics could indicate that the structural distortion of NbO_6 octahedron decreases with the increase in Nd content, which results in the decrease in T_m for SrBi_(2-χ)Nd_χNb_2O_9 ceramics.