Thermal expansion of MNbO4 phases where M=Al, Cr,Fe, Ga

Studies on thermal expansion of the MNbO4 type phases where M=Al, Cr, Fe, Ga have been carried out in the high-temperature X-ray diffraction attachment. In the case of isotypic AlNbO4 and GaNbO4 compounds the structure of which consists of the ReO3 type blocks, the direction of minimal thermal expansion is consistent with the direction in which these blocks spread to infinity. In the case of CrNbO4, the maximal thermal expansion direction is consistent with the [001] direction parallel to which the edge shared octahedra building its structure form infinite chains. FeNbO4 has the highest coefficients of thermal expansion in this group of compounds.