Face-centered cubic (Al1 − xCrx)2O3

We report the discovery of a face-centered cubic (Al1−xCrx)2O3 solid solution [0.60 < x < 0.70] in films grown onto Si substrates using reactive radio frequency magnetron sputtering from Al and Cr targets at 400 °C. The proposed structure is NaCl-like with 33% vacancies on the metal sites. The unit cell parameter is 4.04 Å as determined by X-ray diffraction. The films have a <100> preferred crystallographic orientation and exhibit hardness values up to 26 GPa and an elastic modulus of 220–235 GPa.