A prediction-guided glass-crystallisation strategy for the isolation of new crystalline compounds: SrO-Al2O3-SiO2 as a test case
PITCHER M. 1, COLLINS C. 2, DUNCAN E. 1, RIDOUARD A. 1, FAYON F. 1, VERON E. 1, GENEVOIS C. 1, ALLIX M. 1
1 CEMHTI CNRS UPR3079, Orléans, France; 2 University of Liverpool, Liverpool, United Kingdom
In the context of new oxide materials discovery, glasses (and their parent under-cooled melts) can be considered as ideal precursors for exploratory synthesis: they can be crystallised at substantially lower temperatures that the equivalent ceramic reaction, which allows metastable crystalline solids with unusual and surprising features to be isolated. For example, we recently showed that the crystallisation of YAG glass or melt below 1000°C permits highly nonstoichiometric derivates such as Y3.4Al4.6O12 to be isolated, which are totally inaccessible at the standard ceramic synthesis conditions of 1650°C. When harnessed to apparatus such as laser-coupled aerodynamic levitation, a relatively wide range of compositions can be addressed that is not restricted to classic glass-forming systems. At the same time, computational tools based on crystal structure prediction have recently been developed to guide exploration of complex phase fields. In particular, the probe structure approach allows the identification of compositional regions that are most likely to yield stable crystalline compounds, but it has previously only been deployed alongside ceramic synthesis methods that favour equilibrium products. Here, I will describe how glass-crystallisation (as a non-equilibrium synthesis method) has been coupled to the probe-structure prediction method to isolate a new compound, Sr2Si3O8, from the previously well-explored phase diagram SrO-Al2O3-SiO2, selected as a test case due to its large glass-forming domain and its ability to host functional properties such as luminescence phosphor hosts and transparent ceramics. Sr2Si3O8, which adopts a distorted variant of the Ba2Si3O8 ribbon-type crystal structure, is the first example of a strontium silicate with an extended [SiO4] network. In principle this methodology can be applied to other glass-amenable phase fields to find new crystalline compounds with interesting properties.
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