The wetting behavior and metal-oxide interface interactions in the Er2O3/(Cu-Al) and Er2O3/(Cu-Ti) systems were investigated at 1,423 K in order to evaluate the compatibility of ceramic crucibles with liquid metals, containing active elements. Pure Cu does not wet Er2O3 (Theta approximate to 140 degrees) but the wettability is significantly improved by the addition of Al or Ti. It was established that Er2O3 reacts with Ti and Al dissolved in liquid Cu and the wettable spinel ErAlO3 and ErTiO3 is formed at the interface. The amount of the released Er from the substrate as a result of the reaction and the depth of the reaction zone beneath the drop are controlled by the thermodynamic properties of liquid solutions.