Crystallization of ZrTiO₄ nanocrystals in lithium-alumino-silicate glass ceramics: anomalous small-angle X-ray scattering investigation

We report on anomalous small-angle X-ray scattering (ASAXS) investigations of the formation and structure of nanosized ZrTiO₄ crystals in lithium-alumino-silicate (LAS) glass during heat treatment at 750 °C for different periods of time. For a sample annealed for 30 min, ASAXS measurements near the X-ray absorption edge of Ti and Zr reveal the formation of particles (ZrTiO₄) surrounded by a shell-like region. The sample annealed for 240 min shows the formation of two different types of particles (spherical core-shell: ZrTiO₄ and large spherical particles: LiAlSi ₂O₆). Additionally, ASAXS results allow quantitative determination of the average composition and volume fraction of the nanocrystals, the surrounding region (shell), and the remaining glass matrix. Data analysis reveals the formation of an alumina enriched region around ZrTiO₄. This alumina enriched layer makes the glass network rigid and hinders further growth of ZrTiO₄ nanoparticles. For a prolonged annealing time (240 min), a new phase (LiAlSi₂O₆) is formed additionally, and the (Al/Si) ratio in the shell surrounding the ZrTiO₄ crystals decreases. Moreover, the unannealed sample also shows the formation of a Ti enriched phase during cooling of the samples. The obtained quantitative information helps to understand the crystallization and growth mechanisms of ZrTiO₄ nanocrystals in LAS glass ceramics.