Structural and ferroelectric properties of spray deposited sodium nitrite:poly(vinyl alcohol) composite films

The composite films of sodium nitrite (NaNO₂) and poly(vinyl alcohol) (PVA) have been deposited by spray technique at different substrate temperatures. The x-ray diffraction study revealed structural distortion (b/a ratio) in the composite films. The field-emission scanning electron microscopy images suggest that PVA polymer facilitate the homogeneous distribution of spherical grains of NaNO₂ with less porosity. The grain size is found to increase with the deposition temperature. The study of hysteresis loop characteristics gave optimum P_r at deposition temperature of 200 °C, which may be due to large structural distortion and less porosity. The back switching calculations and the switching characteristics indicate that 180° domains contribute more in the composite than the pure NaNO₂ film. The 1/Є₀(dP/dE)-E curves exhibit two coercive fields correspond to 180° and 90° domains. The composite film also showed improved fatigue characteristics.