Macroscopic and micro-structural aspects of the lithium metaphosphate glass crystallization

The LiPO3 glass crytallization have been investigated according to isothermal and non-isothermal approaches by using various techniques such as thermal analysis, helium pycnometry, scanning electronic microcospy and X-ray powder diffraction. Different experimental procedures have been developed to determine the crystallized volume fraction. The different results are a good agreement and leadto a better comprehension at a “macroscopic” scale of this first order transition. In addition, from “ex-situ” X-ray powder diffraction experiments, the understanding of the diffraction line intensities as a function of the annealing time, at a fixed temperature, has revealed a new metastable crystalline form of LiPO3 (named alpha) stable over a short time range. Attempts for indexing led to a possible monoclinic system close to that reported in literature for the thermodynamical stable variety (named beta). The micro-structure of annealed samples has been discussed in terms of crystallite sizes and lattice micro-distorsions at a nanometer scale. This study based on diffraction line broadening analysis was carried out with the integral breadth method. Finally, from “in-situ” X-ray powder diffraction experiments, evidence was shown that the LiPO3 glass matrix crystallizes first in a metastable LiPO3-alpha form which, in turn, transforms into the beta form.