Crystallization of MgO‐Al₂O₃‐SiO₂‐ZrO₂ Glasses

Abstract

The crystallization of MgO‐Al2O3‐SiO2‐ZrO2 glasses at 1000°C was studied. Isothermal heat treatments of a cordierite‐based glass (2MgO.2Al2O3.5SiO2= Mg2Al4Si5O18) with 7 wt% ZrO2 produced surface crystallization of α‐cordierite and tetragonal ZrO2 (t‐ZrO2). These phases advanced into the glass by cocrystallization of t‐ZrO2 rods in an α‐cordierite matrix with a well‐defined orientation relation. The t‐ZrO2 rods were unstable with respect to diffusional breakup (a Rayleigh instability) and decomposed into rows of aligned ellipsoidal and spheroidal particles. The t‐ZrO2 was very resistant to transformation to monoclinic symmetry. With a similar glass containing 15 wt% ZrO2, surface crystallization of α‐cordierite and t‐ZrO2 was accompanied by internal crystallization of t‐ZrO2 dendrites. Transformation of the dendrites to mono‐clinic symmetry was observed under some conditions.

Mullite and Mullite/ZrO2-7wt.%Y2O3 Powders for Thermal Spraying of Environmental Barrier Coatings

“…8c). The dendritic morphology of these crystals (Ref 21,22) and the XRD results indicate that they correspond to the t-ZrO 2 phase (Fig. 4).…”

Crystallization Behaviour of Zirconia Substituted Lithia-Alumina-Silica Glasses

“…X-ray diffraction data of crystallized glasses are given in Table III. The principal crystalline phases that appeared in glasses G 1 to G 5 glasses G 2 to G 5 were the cubic or tetragonal Zr0 2 polymorph and lithium metasilicate, whereas in the glass Gh ,8-spodumene crystallized as the major phase. These analyses show that with the addition of zirconia, crystallization behaviour of these glasses changed significantly.…”

Solid–liquid interactions: The key to microstructural evolution in ceramics

“…refs. [32][33][34][35][36] . The mechanism of microstructure formation via crystallisation from glasses makes the microstructures of glass ceramics very different from the simple grain structures of most powderderived polycrystalline ceramics.…”