The role of thermal vibrations in transformation of structure transition for sodium nitrate in a restricted geometry

Abstract

The temperature evolution of the crystal structure and dielectric response of a nanocomposite based on porous glasses with an average pore diameter of 7 nm and embedded sodium nitrate in the temperature range of 300–600 K have been studied on heating. The temperature dependences of the amplitudes of thermal vibrations of ions in sodium nitrate nanoparticles are obtained, and the activation energies of sodium hopping conductivity in these nanocomposite materials are determined. The results obtained allow us to state that it is the sharp increase in thermal vibrations that leads to the appearance of the previously observed crossover in the temperature dependence of the order parameter of the structural transition in sodium nitrate nanoparticles at T* ∼455 K and to a decrease in the activation energy of sodium ions hopping conductivity on heating above T*.