Effect of Ta-substitution on the deposition of (K,Na)(Nb,Ta)O₃ films by hydrothermal method

Abstract

Ta substituted (K,Na)NbO 3 films have been deposited at 200 °C on (001)La:SrTiO 3 substrates by hydrothermal method. Film composition continuously changed with increasing the concentration of Ta 2 O 5 in the raw material powder, and X-ray diffraction measurement showed that {001} c -oriented epitaxial (K x Na 1−x )(Nb 1−y Ta y )O 3 films were obtained for all compositions. Microstructural analysis using scanning electron microscopy and transmission electron microscopy revealed that Ta-substitution made {001} c planes dominate on the surface of the film, leading to an improvement in average surface roughness. Film thickness increased with deposition time and eventually saturated. However, the saturated film thickness decreased with increasing Ta/(Nb + Ta) ratio. By evaluating the residual powders synthesized simultaneously with the films, it was found that the formation of the perovskite phase had already started in the very early stage of the deposition process, provided that Ta 2 O 5 powder was present in the source solution.

Effect of Ta substitution on the synthesis of (K,Na)(Nb,Ta)O₃ powders by hydrothermal reaction: Insight into the combination of alkaline solution and raw powder

“…The Ta content in powders was controlled by changing the nominal composition of a mixed powder, C = [Ta ), the ratio of alkaline element of the mixed solution was fixed to 0.9 since our previous works showed that K-rich (K,Na)(Nb,Ta)O 3 films can be obtained at this ratio. 27) The actual chemical composition (: K/(K + Na) and Ta/ (Nb + Ta) ratios) was determined by X-ray fluorescence spectroscopy (PW2404, PANalytical). Crystal structure was investigated by X-ray diffractometry (XRD, Philips X'Pert MRD system, Cu-K¡ 1 radiation).…”