In the master thesis, sodium niobate thin films were prepared by chemical solution deposition. The precursor solution, which served as a reference, was synthesized in an organic solvent. In addition, the sodium niobate precursor was also synthesized in an aqueous solution. To both solutions, 1 mol% of manganese was added as a dopant and the influence of the choice of precursor and heat treatment conditions on the phase composition, microstructure and functional response of the sodium niobate thin film was investigated.
The reference precursor solution was prepared from sodium acetate, niobium(V) ethoxide and diethanolamine in 2-methoxyethanol as solvent. The films were prepared by repeating the deposition of the solution on a platinized silicon substrate five times by spin-coating, drying and pyrolysis with the final heating at 650 °C. The films crystallized in the perovskite phase. The film thickness was about 150 nm and the surface grain size was about 300 nm at the heating rate ≤ 12.5 K/s. The heating rate slightly affected the average grain size and size distribution. Using a piezoelectric module of the atomic force microscope, we confirmed that the films showed local piezoelectric and ferroelectric responses.
The aqueous precursor solution was prepared from sodium nitrate and ammonium niobium oxalate hydrate with the addition of 1 wt% polyvinyl alcohol to improve substrate wetting. Final annealing of the films after applying the solution five times resulted in crystallization of the Na2Nb4O11 phase, regardless of the heating rate. The films crystallized in the perovskite phase only when they were annealed after each deposition of the solution onto the substrate, followed by drying and pyrolysis steps, i.e., a total of five times at 600 °C. The thickness of the films was about 100–140 nm, and the surface grain size was about 350 nm. The samples exhibited weak piezoelectric and ferroelectric behaviour, which was slightly improved by the addition of manganese.
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