Evidence of epitaxial growth of high-quartz solid solution on ZrTiO4 nuclei in a Li2O-Al2O3-SiO2 glass

The early stage of crystallization of a glass with the composition 7.6 Li2O - 0.2 Na2O - 0.1 K2O - 1.9 MgO - 0.3 BaO - 1.2 ZnO - 12.7 Al2O3 - 69.6 SiO2 - 4.2 TiO2 - 1.8 ZrO2 - 0.4 Sb2O3 (mol %), suitable for the production of zero thermal expansion glass-ceramics is reported. Thermal treatment at 740 °C for 24 h resulted in the formation of Zr1-xTi1+xO4 crystals and close to them, high-quartz solid solution crystals (lithium aluminosilicate solid solution of high-quartz structure) were formed. TEM studies showed tetragonal Zr1-xTi1+xO4 crystals with a puck-like shape, and on their flat sides, high-quartz solid solution crystals were precipitated, squeezing the “Zr1-xTi1+xO4 patty” in-between two halves of the “lithium-alumosilicate bun”. Selected area electron diffraction showed a distinct crystallographic relationship between these two crystal lattices. High resolution TEM micrographs indicate that the lattice planes observed in the Zr1-xTi1+xO4 crystal continue into the high-quartz solid solution crystal. This is evidence for epitaxial growth of the lithium-alumosilicate with high-quartz structure on the Zr1-xTi1+xO4 crystal. Epitaxial growth within glass-ceramics has hardly been shown up to now.