Crystallographic assessment and thermal expansion fine-tuning of quartz solid solutions in the ZnO–MgO–Al2O3–SiO2 system

Abstract

Glass powders with compositions within the ZnO–MgO–Al₂O₃–SiO₂ system (without the addition of nucleating agents) were synthesized by spray-drying and carefully crystallized to obtain stuffed quartz solid solutions (Qz-ss). The substitution of Zn by Mg causes an increase in the crystallization temperature and the composition of Qz-ss varies during their formation, highlighting a nonisochemical precipitation with respect to the parent glass. A change from a low-temperature modification of Qz-ss to a high-temperature modification was visible for Qz-ss containing 80 or 90 mol% SiO₂. The high-temperature modification of Mg- and (Zn,Mg)-Qz-ss displays negative thermal expansion for SiO₂ content equal to 90 mol%, but a positive one for 80 and 67 mol%. In contrast, the high-temperature modifications of Zn-Qz-ss show a negative thermal expansion for the three SiO₂ contents studied. The properties of (Zn,Mg)-Qz-ss containing 67 mol% SiO₂ cannot be predicted by a linear interpolation between Zn-Qz-ss and Mg-Qz-ss. A (Zn,Mg)-Qz-ss with zero thermal expansion was crystallized by modulating SiO₂ content and Mg/Zn ratio.