Lattice contraction and cation ordering of ZrTiO4 in the normal-to-incommensurate phase transition

Abstract

It is known that microwave dielectric ZrTiO4 undergoes a normal-to-incommensurate phase transition (NICPT) near 1125 degreesC. The role of the cation ordering and its relation to the anomalous lattice contraction observed in the NICPT were studied by x-ray diffraction and Raman scattering of ZrTiO4 specimens prepared employing various cooling rates between 1250 and 1000 degreesC. It was shown that the lattice parameter b underwent a substantial change even if the long-range cation ordering was absent. Analysis of the Raman spectra indicated that the compositional fluctuation-induced line broadening was mainly responsible for the extrapolated linewidth at 0 K, suggesting that the observed lattice contraction was initiated by the local short-range cation ordering. Based on thermodynamic arguments, the anomalous lattice contraction of ZrTiO4 was attributed to a direct consequence of the gradient coupling between the two order parameters that describe a compositional modulation and a displacive modulation in the NICPT. (C) 2001 American Institute of Physics.