Electrically driven wetting of high-entropy (Zr1/3Hf1/3Ce1/3)1-x(Y1/2Gd1/2)xO2-δ ceramics by molten Cu

For the first time, the wettability of fluorite-type high-entropy (Zr1/3Hf1/3Ce1/3)1-x(Y1/2Gd1/2)xO2-delta (delta = 0.05-0.3) ceramics by molten Cu under a direct current (DC) was investigated. The wetting behavior depended noticeably on the stoichiometry (x = 0.1-0.6) of the metal components in (Zr1/3Hf1/3Ce1/3)1-x(Y1/2Gd1/2)xO2-delta. The initial contact angle increased with x. For x >= 0.4, DC application improved the wettability, and the final contact angle decreased with increasing x. The wettability improvement was mainly attributed to the diffusion of high-entropy metal components into the Cu melt and the formation of an interfacial product. The relatively weak Ce-O and Gd-O bonds were dissociated more easily, and Ce and Gd diffused more rapidly than Zr, Hf and Y and thereby influenced the wettability more prominently. This work is expected to advance the understanding of interfacial physicochemical interactions between metal melts and high-entropy oxides and provide a reference for joining high-entropy oxides with metals under an electric field.