Thermochemical data for ceramic materials are essential both for understanding fundamental solid state chemistry (structure, bonding, and crystal chemical systematics, as well as vibrational, magnetic, optical, and electronic phenomena) and for predicting phase equilibria, materials compatibility, and reactivity. This Hugh M. Huffman Memorial Award Lecture describes recent advances in high-temperature oxide melt calorimetry in the University of California Davis Thermochemistry Facility and illustrates its application to three problems of technological significance: the relative stability of alpha- and beta -silicon nitride; the inversion of stability of alpha- and gamma -alumina at the nanoscale, and the ion exchange of cesium and sodium in silicotitanate zeolite-like materials proposed as hosts for radioactive waste.