Effect of aliovalent substitution on the crystal distortion and negative thermal expansion properties of Zr2SP2O12

Abstract

We evaluated the thermal expansion of newly synthesized Zr2-xMxSyP2O12-δ, with zirconium (IV) ion (Zr4+) partially substituted by five aliovalent ions (aluminum (III) ion (Al3+), iron (III) ion (Fe3+), yttrium (III) ion (Y3+), niobium (V) ion (Nb5+), and gadolinium (III) (Gd3+)) ion. High-temperature X-ray diffraction patterns showed that Zr2-xMxSyP2O12-δ had the same negative thermal expansion as Zr2SP2O12 and that the volumetric coefficient of thermal expansion (αv) could be controlled by ion substitution. The lowest αv value obtained for Zr1.7Y0.3SP2O12-δ at 373–453 K was approximately −117 ppm/K. Rietveld's analysis showed that aliovalent substitution could make the crystal structure of Zr2SP2O12 at 303–373 K distorted and the lattice volume larger. In addition, multiregression analysis demonstrated that ZrO6 octahedral volume and certain bond angles in the crystal structure were related to the lattice volume.