Hydrothermal crystal growth of fresnoite

The growth of fresnoite, Ba2TiSi2O8, by hydrothermal synthesis has led to spontaneous generation of large, (4–5 mm) optically clear crystals from 6 M KF mineralizer solutions. Growth was achieved at relatively low synthesis temperatures (575 °C) comparative to fresnoite synthesis by Czochralski or flux methods. Bulk crystal growth possibilities were explored by transport reactions performed in both fluoride and hydroxide mineralizers with 25–45 °C temperature gradients. Growth rates of 0.14×0.19×0.22 mm3/week were established in 6 M KOH, which is significantly slower than standard hydrothermal rates of 1 mm/week. Although relatively slow, the hydrothermal method has been demonstrated as a synthesis route to high quality single crystals of fresnoite.