Elastic Properties and Thermal Expansion of NaNO₃ Single Crystal

Abstract

All components of elastic stiffness and compliance in NaNO₃ crystal have been determined from room temperature to 300°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 λ-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 D_3d⁵.