: A mathematical model is derived to elucidate the dominant mechanism governing film formation. It leads to a relation between film thickness and film radius spreading with time. Inclusion of evaporation and shear stress was made with extension to non-Newtonian fluid. The advantages and disadvantages of this process with applications are reviewed.

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Bismuth sodium titanate, Bi 0•5 Na 0•5 TiO 3 (BNT) is considered to be an excellent candidate for a key material of lead-free dielectric ceramics. In this study, we propose the dielectric and optical study of single phase BNT powder prepared by solid-state reaction route. The phase formation and structural study were done by X-ray diffraction (XRD) which shows well developed crystallite with a pure perovskite phase. The ceramic was sintered at different temperatures from 1050 • C to 1175 • C to study the effect of sintering temperature on the morphology and density. It was found that the sample sintered at 1150 • C shows the highest density. The microstructure of the ceramic was investigated by scanning electron microscopic (SEM) technique. The temperature-dependent dielectric study of the sample sintered at 1150 • C was done in the frequency range of 50 kHz-1 MHz which shows a diffuse phase transition. The piezoelectric constant (d 33) was found to be 41 pCN −1. The P-E hysteresis loop confirms the ferroelectric behaviour in the ceramic. The UV-Vis spectrum indicated that the Bi 0•5 Na 0•5 TiO 3 ceramic has an optical band gap of 2•94 eV.

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