Order-disorder transition in Nd2-yGdyZr2O7 pyrochlore solid solution:: An X-ray diffraction and Raman spectroscopic study

Powder X-ray diffraction (XRD) and Raman spectroscopic study of order-disorder-phase transition with increase in the content of Gd in Nd2-yGdyZr2O7 solid solution is being reported. It has been observed from Rietveld analysis that with increase in concentration of Gd in Nd2-yGdyZr2O7, the value of the x parameter of the 48f oxygen changes from 0.332(1) to 0.343(1) with a sudden change in the slope for y = 1.8, which indicates that the structure is transforming from ordered pyrochlore to disordered pyrochlore. In addition to that a Sudden and drastic change in the Raman spectra including changes in the position and width of several Raman modes beyond y >= 1.8 has also been observed which has been correlated with increasing disorder. Based on these studies, it is suggested that there is a discontinuous order-disorder transition from 'perfect pyrochlore' to 'defect pyrochlore' phase in Nd2-yGdyZr2O7 solid solution. (C) 2007 Elsevier Inc. All rights reserved.