Influence of powder supply on radio-frequency power stability and compositional uniformity in near-stoichiometric LiTaO 3 crystal grown by double-crucible Czochralski method

Abstract

Near-stoichiometric LiTaO 3 (SLT) crystals were grown from a Li-rich solution by the double-crucible Czochralski (DCCZ) method with and without an automatic powder supply system, to investigate influence of the powder supply system on the stability of radio-frequency (RF) power and the compositional uniformity of the grown crystal. To maintain a constant crystal diameter, the RF power is decreased during crystal growth without the powder supply system, while it is kept almost constant during crystal growth with the powder supply system. The Curie temperature of an SLT crystal grown with the powder supply system was almost constant along both growth and lateral directions, and the [Li]/([Li]+[Ta]) ratio in this crystal was estimated to be 0.4992 by comparing its Curie temperature with those of ceramics of known composition. In contrast, in an SLT crystal grown without the powder supply system, the Curie temperature was observed to increase with increase in distance from the top of the crystal; therefore, the crystal composition was thought to gradually change due to the change of solution composition during crystal growth. In SLT crystal growth, the DCCZ method using the automatic powder supply system provided an almost constant thermal condition during crystal growth as well as compositional uniformity throughout the SLT crystal.