Microstructure of Bi3-xNdxTiNbO9 Bismuth Layer-Structured Ceramics

The microstructure of Bi3-xNdxTiNbO9(NBTN-x, x = 0.00 ∼ 0.75) ceramics were studied by X-ray diffraction and Raman spectroscopy. Bi3TiNbO9 ceramics bear orthorhombic phase, while the sample with Nd3+ content of 0.75 was determined to be tetragonal phase by X-ray diffraction. Raman spectra revealed that Nd3+ substituted for the Bi3+ in A site rather than in the [Bi2O2]2+ layer, unlike in the case of La3+ doping in Bi3TiNbO9. The tilt of the Ti/NbO6 octahedra decreased with increasing x. Based on the XRD data and Raman results, the overlap of the Raman modes 310 and 360 cm−1, which was ascribed to O-Ti-O bending, demonstrated that the crystal structure underwent the phase transition from orthorhombic to tetragonal when x = 0.75.