Synthesis and Thermal Stability of Cubic ZnO in the Salt Nanocomposites

TL;DR

This study reports the synthesis of metastable cubic ZnO nanoparticles within a salt matrix and investigates their thermal stability and phase transition to wurtzite ZnO using calorimetry and X-ray diffraction.

Contribution

It presents a novel synthesis method for cubic ZnO nanoparticles and provides the first experimental analysis of their phase transition at ambient conditions.

Findings

Cubic ZnO was successfully synthesized at high pressure and temperature.

The phase transition from cubic to wurtzite ZnO occurs between 370-430 K.

The enthalpy change of the transition at 400 K is -10.2 kJ/mol.

Abstract

Cubic zinc oxide (rs-ZnO), metastable under normal conditions, was synthesized from the wurtzite modification (w-ZnO) at 7.7 GPa and ~800 K in the form of nanoparticles isolated in the NaCl matrix. The phase transition rs-ZnO \rightarrow w-ZnO in nanocrystalline zinc oxide under ambient pressure was experimentally studied for the first time by differential scanning calorimetry and high-temperature X-ray diffraction. It was shown that the transition occurs in the 370-430 K temperature range and its enthalpy at 400 K is -10.2 \pm 0.5 kJ mol-1.