The fabrication of alkaline-earth-bearing ceramics by the oxidation of solid, metal-bearing precursors

A relatively novel method for fabricating shaped, alkaline-earth(AE)-bearing ceramic components is the oxidation of solid, AE-metal-bearing precursors. Ba, Sr, Ca, and Mg are relatively ductile metals that, when present in sufficient quantities, can endow a precursor with the plasticity required for deformation processing or machining. These malleable AE metals can be oxidized at a relatively rapid rate at less than or equal to 500 degrees C. The resulting AE oxides can react with other metals and/or oxides in the precursor to form multi-component ceramic compounds at modest temperatures. Another important and unusual feature is that the molar volumes of most AE metals are larger than the molar volumes of corresponding AE oxides, whereas the opposite is true for other elements (e.g., V-m[Ba] > V-m[BaO2] and V-m[Si] < V-m[SiO2]). As a result, the phase content of AE-metal-bearing precursors can be tailored such that ceramic parts that retain the precursor shape and dimensions can be produced. The fabrication of AE aluminosilicates, cerates, cuprates, ferrites, phosphates, and titanates is discussed.