Synthesis and thermal stability of cubic ZnO in the salt nanocomposites

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