Low-temperature thermal expansion of rock-salt ZnO

Lattice parameter of metastable high-pressure phase of zinc oxide, rock-salt ZnO was measured in the 10-300 K temperature range using synchrotron X-ray powder diffraction. No phase transition was observed down to 10 K. The lattice parameter of rock-salt ZnO was found to increase from 4.266 {\AA} in the 10-80 K range up to 4.2752(3) {\AA} at 298 K, while the volume thermal expansion coefficient increases from slight negative values below 40 K up to 4.77\times10^-5 K^-1 at 298 K.