Thermal expansion of pyrolusite, β-MnO2; a synchrotron X-ray diffraction study

Abstract

High resolution synchrotron X-ray powder diffraction (S-XRD) methods have been used to study the temperature dependence of the structure of β-MnO2 between room temperature and 400 °C. Rietveld analysis of the S-XRD data provided accurate and precise until cell parameters from which the thermal expansion coefficients (TEC) were determined, αa = 7.8 × 10−6 K−1 and αc =7.2 × 10−6 K−1. The difference in the anisotropy in the TEC and the temperature dependence of the distortion of MnO6 and TiO2 suggests MnMn interactions across the shared edge are significant.