Diopside-Ca-Tschermak clinopyroxene based glass-ceramics processed via sintering and crystallization of glass powder compacts

The suitability of three new glass compositions for producing diopside-Ca-Tschermak clinopyroxene based glass-ceramics (GCs) was investigated. With respect to the formula of diopside, the first investigated composition resulted from the substitution 0.2(Si⁴⁺ + Mg²⁺) ↔ 0.4 Al³⁺, which leads to a composition of 80 mol.% diopside and 20 mol.% Ca-Tschermak. The substitutions in the second compositions were 0.25(Ca²⁺ + Si⁴⁺) ↔ 0.25(Y³⁺ + B³⁺) and 0.2(Si⁴⁺ + Mg²⁺) ↔ 0.4Al³⁺, and in the third composition 0.2Ba²⁺ ↔ 0.2Ca²⁺ and 0.2(Si⁴⁺ + Mg²⁺) ↔ 0.2(B³⁺ + Al³⁺). The influence of these substitutions on glass crystallization and the properties of the GCs produced between 850 and 1000 °C was experimentally investigated. The experimental results showed that the easily cast glasses, after melting at 1580 °C for 1 h, are prone to surface crystallization. Augite is predominantly crystallized, but Ca- and Ba-aluminosilicates can also form, according to the substitutions. The stability of the assemblage of the crystalline phases over a wide temperature range (850-1000 °C) and prolonged heat treatment (up to 50 h) and the properties of the produced GCs indicate a high potential of these compositions for several functional applications.