A new solid electrolyte, Sc1/3Zr2(PO4)(3), with a trivalent ion conductivity similar to that of the Sc-2(WO4)(3)-type tungstate series is investigated. It is demonstrated that, unlike the tungstate-based electrolyte, the phosphate-based electrolyte can be used in a variety of atmospheres, including a reducing one. The Figure is an SEM image of Sc deposited at the cathodic surface after electrolysis.