The crystal structure of rutile as a function of temperature up to 1600°C

Abstract

Abstract The crystal structure of rutile (TiO2) has been studied at high temperatures up to about 1600°C based on sets of single crystal X-ray diffraction intensities collected on a four-circle diffractometer. The thermal expansion coefficients for the a- and c-axes in the measured temperature range were αa = 8.9(1) × 10−6 °C−1 and αc = 11.1(1) × 10−6 °C−1, respectively. The thermal response of the octahedra about Ti is such that the thermal coefficient for the four short equatorial Ti – O bonds was 8.4(3) × 10−6 °C−1 and for the two long apical Ti – O bonds 11.5(3) × 10−6 °C−1. The rate of thermal expansion of the octahedral shared edge is relatively large under ∼ 1200°C, while it becomes small above ∼ 1200°C. An l to lo ratio, which we denote shrinkage index, however, decreases with the raise of temperature (l = the length of the shared edge at a temperature; lo = the edge length of a regular octahedron having the same volume as the Ti octahedron has at the same temperature).