Study of thermal decomposition of (K_0.5Na_0.5)NbO₃ thin-films precursors with different amounts of alkali-acetate excess

Abstract

Liquid precursors of (K_0.5Na_0.5)NbO₃ thin-films were prepared from alkali acetates and niobium ethoxide in 2-methoxyethanol solvent either in a stoichiometric ratio or with 5 or 10 mole % of potassium or sodium acetate excess. Fourier-transform infrared (FTIR) spectroscopy of the dried precursors confirmed the presence of acetate and hydroxyl groups. Thermaldecompositions of the as-dried precursors in air occurred gradually. Between roomtemperature and ~200 °C, the weight loss of a few per cent was due to the evaporation of residualsolvents. The major mass loss was due to thermal oxidation of organic group with the major exothermic events at about 250 °C and 450 °C, almost 200 °C below the onset of the chemical decomposition of alkali acetates, indicating that a heterometallic complex was formed in solution, in agreement with FTIR analysis. Both the amount and to a lesser extent the choice of alkali-acetate excess influenced the thermal decomposition of the organic groups predominantly in the temperature interval between ~200 °C and ~400 °C.