Potassium tantalate niobate (KTN) KT0.65Nb0.35O3 powders and thin firms of perovskite structure were prepared through set-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 degrees C, and then completely transformed to perovskite at 750 degrees 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 (100) and (110)substrates and highly oriented KTN films on R-plane sapphire and LaAlO3 (012) substrates. The chemical composition of the KTN powders and thin films is in good agreement with the atomic ratio of the starting materials.