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(1 − x )(Na1− y K y )NbO3- x BaTiO3 (abbreviated as NKN-BT, x = 0.1, 0.2; y = 0.01, 0.05) ceramics were synthesized by the solid-state reaction method. Powder x-ray diffraction analysis in combination with the profile refinement method was employed for quantitative phase analysis and structural refinement. The x-ray diffraction study shows that phase transition occurs from tetragonal to distorted cubic with the compositions between x = 0.1 and x = 0.2. The spatial arrangements of the electron distribution and bonding nature of the samples have been analyzed through the maximum entropy method. The optical band gap energy of the prepared solid solutions has been determined using UV-visible spectrophotometry. The optical band gap energy of the solid solutions decreases with the increase in BaTiO3 content. The elemental composition of these ceramics has been studied using energy dispersive x-ray analysis and the microstructure has been examined by scanning electron microscopy. The piezoelectric coefficient ( d 33 ) measurement of the ceramics shows the enhancement of piezoelectric properties in the tetragonal phase. The maximum value of the piezoelectric coefficient ( d 33 ) obtained for the solid solution is 120 pC/N. With increasing BaTiO3 content in the solid solutions, the ferroelectric behavior weakens.
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