The conversion of metals into their oxides as a result of heating to a high temperature WordNet 3.0 & Open English WordNet

Calcination is thermal treatment of a solid chemical compound whereby the compound is raised to high temperature without melting under restricted supply of ambient oxygen, generally for the purpose of removing impurities or volatile substances and/or to incur thermal decomposition. Wikipedia

Manufacturing Wikidata

The process of calcining: heating a substance to a high temperature, but below its melting point, to bring about thermal decomposition. Wiktionary

The process of calcining. Wiktionary (translation)