ELASTIC PROPERTIES AND THERMAL-EXPANSION OF NANO3 SINGLE-CRYSTAL

All components of elastic stiffness and compliance in NaNO3 crystal have been determined from room temperature to 300-degrees-C. They show anomalies associated with the phase transition in the vicinity of T(c). Thermal expansion coefficients parallel and perpendicular to the three-fold axis exhibit lambda-type temperature dependence near T(c). The phase transition of NaNO3 is discussed on the basis of a phenomenological theory with an order parameter related to an irreducible representation at k8 point of D3d5.