Liquid phase epitaxially grown crystals are prepared in a tilt tube apparatus pivotable about a pivoting arrangement (21). The apparatus comprises a silica crucible (10) within a silica reaction tube (11) having a palladium diffused hydrogen atmosphere which is heated by electric furnace (12). The crucible (10) is in contact with a silica rod (13) which is connected through a flexible coupling (15) to a transducer (14) which draws power from a power oscillator (17). Vibrations are thereby induced in the crucible (10) during preparation of a crystal.
