Effect of alumina content on the crystal structure, lattice thermal expansion and thermal conductivity of aluminium-rich spinel solid solutions

Magnesium alumina spinel solid solutions with different chemical compositions were synthesized and their crystal structures were refined using the Rietveld method based on synchrotron radiation X-ray diffraction (XRD). A linear relationship between the lattice parameters a0 and x in Mg1-xAl2+2/3x□1/3xO4 was established, the thermal stability and lattice thermal expansion of the solid solutions by in-situ high temperature XRD were investigated. Alumina was eliminated from the high-solubility alumina-rich spinel solid solution to form corundum and a lower-solubility alumina-rich spinel solid solution. The relationship between a0 and temperature is expressed by a quadratic polynomial. The thermal conductivity of Mg1-xAl2+2/3x□1/3xO4 decreased almost linearly with an increase in x, which is attributed to the stronger point-defect scattering effect induced by the difference in atomic mass and cation radii and the increase in cation vacancies as alumina dissolves in spinel. •Refined the cell parameters of the alumina rich solid solutions.•Established the relation between cell parameters vs. solubility.•Investigated the thermal expansion behavior by in-situ high temperature XRD.