Composition-structure-property relationship in tectosilicate solid solutions synthesized from glass

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Despite the intensive research efforts that have been invested in the fields of silicate materials and glass crystallization, knowledge gaps still persist and prevent full understanding and detailed assessment of possibly advantageous materials systems in glass-ceramic technology. With this project, we aim at closing those loopholes through a fundamental composition-structure-property investigation, concentrating on three specific tectosilicates, i.e. solid-solutions of cristobalite, quartz and leucite that have been selected due to their technological relevance, their development potential and their experimental underdetermination. The objective is to be achieved by taking advantage of the non-equilibrium, kinetically frozen-in state of glass as a starting material, since it allows upon controlled reheating to explore thermodynamically metastable crystalline phases otherwise impossible to synthesize. Thereby the approach follows the Ostwald's rule of stages in accessing the least stable polymorph (solid solution) first. In terms of glass formation, experiments are targeted to prepare the widest possible range of relevant chemical components and concentrations by expanding melt-quenching with the sol-gel spray-drying route. On the one hand, the working group has established appropriate instrumentation for glass preparation and structural characterization during crystallization. Through it, insights will be gained into the evolution of desired solid solution crystals and their structure by performing measurements at ambient, as well as in-situ at high and cryogenic temperatures (mainly XRD). On the other hand, the project aims at fully understanding the crystallographic constraints of the prepared solid solution crystals including a clear assignment or divergence to known crystal polymorphs as well as their transformation behavior. In terms of the glass-ceramic technology, the objective is to gain knowledge on possibly advantageous systems and the development potential of these phases by a detailed assessment of relevant properties, such as thermal expansion.