PREPARATION OF KTAO3 AND KNBO3 SOLID-SOLUTIONS THROUGH SOL-GEL PROCESSING

Potassium tantalate-niobate solid-solution (KTN) powders and thin films were prepared from metallo-organic compounds through sol-gel processing. The KTN precursors were chemically modified and then prehydrolyzed with various concentrations of water. The stability of the modified solutions and the effects of prehydrolysis on the crystallization are discussed. Powder gels were obtained by exposing the solution to the atmospheric water, hydrolyzing the solutions. Alternatively, thin films were deposited on fused silica, silicon, sapphire, MgO, and SrTiO3, using the spinning technique. The pyrolysis and crystallization of KTN powders and films were investigated by differential thermal analysis, thermogravimetric analysis, and X-ray diffraction. The effects of substrate and other processing parameters on the crystal structure of the KTN phases were also investigated. KTN powders crystallized into a perovskite phase regardless of the processing conditions. The crystal structure of the KTN thin films had a strong dependency on the crystal structure of the substrates, while other processing parameters played smaller roles. Pyrochlore KTN was the major phase that crystallized on fused silica and silicon, whereas oriented perovskite KTN was obtained on single-crystal MgO and SrTiO3.