ABSTRACT
Scandium molybdate is the first obtained stable material with negative coefficient of thermal expansion. An anisotropic thermal expansion occurs as the result of a decrease in the sizes along two axes at the expense of rotation of polyhedral parts and an increase along the third axis. For scandium molybdate thermodynamically stable are monoclinic phase in the region of low temperatures and orthorhombic phase in the region of high temperatures. In general the formation enthalpy of monoclinic phase is lower than of the orthorhombic phase; however, the orthorhombic phase is preferable from the point of view of entropy. In the case of the formation of a two-phase system, the question arises about the distribution of scandium and gadolinium atoms over these phases. The paramagnetic component of magnetic susceptibility obeys the Curie–Weiss law over the whole temperature range and for all the concentrations.
