THE GROWTH OF POTASSIUM TANTALATE NIOBATE (KTa_xNb_(1-x)O3) SINGLE CRYSTAL BY VERTICAL BRIDGMAN METHOD

摘要

Growth of potassium tantalate niobate (KTa_xNb_(1-x)O3) single crystals by the vertical Bridgman (VB) method was investigated. KTN crystals were grown using a KTaO3 seed and K-rich raw materials in a platinum crucible in air. When raw material with an atomic ratio of Ta to Nb of 65:35 was used, a KTN crystal could be obtained in which the proportions of Ta and Nb varied widely. Colorless transparent cubic KTN crystallized above the seeding interface, where the atomic ratio of Ta to Nb was 89:11. It was found that this colorless transparent region was a single crystal. The color of the crystal changed to milky white and finally to powder-like white, and small cracks were observed following the milky white region. The proportions of Ta and Nb in the grown crystal gradually changed with the progress of growth, and the terminal of the crystal was tetragonal KTN. The tendency of the composition to change qualitatively obeys the binary phase diagram of KTa03-KNb03.