Structural, optical and electrical properties of La - Mg co-substituted Bi0.5 Na0.5 TiO3 dielectric

Lead free La-Mg co-substituted Bismuth Sodium Titanate (Bi
0.5
Na
0.5
TiO
3
; BNT) dielectric ceramic was synthesized by conventional solid-state reaction (SSR) route. The effects of La-Mg on the microstructural, optical, and electrical properties of BNT were systematically studied. The microstructure of Bi
0.47
La
0.03
Na
0.50
Ti
0.97
Mg
0.03
O
3
showed irregular shape surface grains with an average size of 2.37 ± 0.8 μm. The X-ray diffraction analysis of the co-substituted BNT revealed the formation of single phase rhombohedral R3c structure. An approximately 10% reduction in direct band gap to ~2.9 eV after La–Mg co-incorporation makes this compound a promising candidate for optoelectronic applications as compared to BNT (~3.2 eV). The frequency dependent complex impedance spectroscopic measurement revealed a moderate enhancement in dielectric constant along with a reduction in dielectric loss of BNT after the co-substitution. The frequency and temperature dependent variations in permittivity and loss tangent were explicated in terms of various types of polarization relaxation.