A sealing composition for ceramic discharge vessels is described. The sealing composition contains about 20 to about 40 mole percent MgO, about 20 to about 45 mole percent Y.sub.2O.sub.3, and about 20 to about 60 mole percent Al.sub.2O.sub.3 and has a melting point of less than about 1800.degree. C., and preferably from about 1700.degree. C. to about 1800.degree. C. The sealing composition may be used for making ceramic-to-ceramic or ceramic-to-metal seals in ceramic discharge vessels.