Structure and dielectric behavior of Nd-doped BaTiO3 perovskites

The structure and dielectric behavior of Ba1 − xNdxTiO3 perovskites fabricated by conventional solid state mixed method were investigated. Phase transition behavior appeared from tetragonal to cubic structure with increasing Nd-doping level by XRD results. As the doping concentration increased, in the whole Raman spectra range except 848 cm−1 peak, the Raman intensities of doped BaTiO3 gradually decreased and the peaks became weaker and broader indicative of tetragonal to cubic phase transition. The appearance of the band at 848 cm−1 can be ascribed to the internal deformation/distortion of the TiO6 octahedra and the Nd3+–barium vacancy pairs. Based on the XPS narrow-scan spectra of Ti 2p, binding energy of Ti 2p3/2 decreased with increasing Nd concentration showing the variation of the valence state of Ti ions, i.e. Ti4+ → Ti2+. Nd3+ addition downshifted the temperature of the dielectric maximum and decreased the grain sizes. And the permittivity of doped BaTiO3 ceramics increased with decreasing grain sizes and a maximum value was attained at a size of 0.8–1 μm. The internal stress showed obvious effects on the permittivity of fine-grained ceramics, confirmed by doped BaTiO3 at x = 0.01. Compared with the relaxor ferroelectrics, these samples showed normal ferroelectrics and first-order type phase transition behavior. The TC − T0 (>0) deviation increased with Nd doping indicating the increasing effects of extrinsic non-ferroelectric phase on dielectric properties.