Preparation of potassium tantalate niobate through sol–gel processing

Abstract

Potassium tantalate niobate (KTN) KTa_0.65Nb_0.35O₃ powders and thin films of perovskite structure were prepared through sol–gel processing. A homogeneous and stable precursor solution was obtained from tantalum ethoxide, niobium ethoxide, and potassium ethoxide in absolute ethanol with a key additive of acetic acid. Powder gels were obtained by exposing the solution to atmospheric water, thus hydrolysing the solution. The precursor powder crystallized to pyrochlore at 600 °C, and then completely transformed to perovskite at 750 °C. Alternatively, thin films were deposited on quartz glass, silicon, sapphire, yttria-stablized ZrO₂, LaAlO₃, SrTiO₃ and platinum-coated silicon plates, using the spinning technique. The crystal structure of the KTN thin films showed a strong dependency on the crystal structure of the substrates. Crack-free and transparent epitaxial KTN thin films were successfully prepared on SrTiO₃ (1 0 0) and (1 1 0) substrates and highly oriented KTN films on R-plane sapphire and LaAlO₃ (0 1 2) substrates. The chemical composition of the KTN powders and thin films is in good agreement with the atomic ratio of the starting materials.