The crystal structures of stuffed derivatives of quartz within the Li 1-x Al 1-x Si 1+x O 4 system have been refined by Rietveld analysis of powder synchrotron X-ray diffraction (XRD) data. Our results reveal an Al-Si order-disorder transition at x = ~0.3 and a β-α displacive transformation at x = ~0.65. Structural variations across the series result from an interplay of three mechanisms: tetrahedral tilting associated with Al-Si order-disorder; Li positional disorder along structural channels parallel to c; and tetrahedral rotation related to the β-α transition. At both microscopic (local bonding) and macroscopic (spontaneous strain) scales, the substitution of Li + and Al 3+ for Si 4+ closely mimics temperature in its effect on the quartz framework.
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Xu et al. (2000) studied this question.