Structural study of Bi2O3-ZnO-Nb2O5 based pyrochlores

The cubic pyrochlore structure of Bi1.5Zn1.0Nb1.5O7 was investigated. The crystal chemical formula of this material was determined as Bi1.5Zn0.5(Zn0.5Nb1.5)O7 by comparing the calculated theoretical X-ray diffraction intensities with the observed ones. Crystal structure parameters were refined by Rietveld method. The (Bi1.5−2yZn1+2yNb1.5)O7−y crystalline samples were also examined by Raman spectroscopy to look for further short range structural information. The results show that the Nb–O and Zn–O stretching modes in the B site oxide octahedral almost do not change with the chemical constitution changing. It is reasonable that the movable Zn2+ is inclined to occupy B site first and then enter into A site after the B site was stuffed.