Lanthanum distribution and dielectric properties of Bi3−xLaxTiNbO9 bismuth layer-structured ceramics

Single phases of Bi3−xLaxTiNbO9 (LBTN-x, x = 0.00–1.00) ceramics were studied by dielectric and Raman spectroscopy. With different La contents (x), LBTN-x ceramics exhibit distinct ferroelectric properties. When x = 0.00, 0.25, 0.50, LBTN-x are normal ferroelectrics, while when x > 0.50 they become relaxor ferroelectrics. Raman spectra were used to explain this relaxor phenomenon, which resulted from the fact that La3+ begin to partly substitute the Bi3+ in Bi2O2 layers when the La content x > 0.50.