GPa and 1450-1650 K in the wide concentration range . It has been found that the widest (x ≤ 0.8) compositional range for the existence of single-phase rock-salt solid solutions is observed for the NiO-ZnO system, due to smaller radii and the energetic preference of octahedral coordination over tetrahedral . rs-Co 1-x Zn x O, rs-Fe 1-x Zn x O and rs-Mn 1-x Zn x O solid solutions can only be quenched to ambient conditions with much lower ZnO content. However, the use of nanocrystalline w-ZnO allows single-phase rs-ZnO to be quenched from 7.7 GPa and 770-820 K .