Dielectric, ac-impedance and modulus spectroscopic studies of nano-crystalline Bi_0.5Na_0.5TiO₃ synthesized by using one pot glycine assisted solution combustion from inexpensive TiO₂

Nano-crystalline Bi_0.5Na_0.5TiO₃ (BNT) ceramic has been successfully synthesized for the first time by solution combustion synthesis using glycine as the fuel, inexpensive solid TiO₂ powder as the raw material, and metal (Bi and Na) as nitrates. Phase formation, the crystalline nature, morphology, and chemical purity of the fabricated BNT were investigated with TGA, XRD, SAED patterns, SEM, TEM, and EDX analyses. TG/DTA analysis of the dry powder gives pre information about the formation of final product around 900 °C, which is a relatively lower temperature than other conventional ceramic methods. XRD patterns confirmed the formation of a single phase of all the sintered ceramics. The bright-field TEM image revealed that the particle size was in the range of 20–35 nm, which was in near agreement with the average crystallite size obtained from XRD. SEM images of the sintered BNT ceramics showed the average grain sizes were in the range of 150 nm–0.5 µm. EDX studies showed the presence of bismuth, sodium, titanium, and oxygen, which confirmed the stoichiometry and purity of the ceramics. The AC conductivity spectrum obeyed the Jonscher power law. The natures of relaxation behavior of the ceramics were rationalized by using impedance and modulus spectroscopy. The dielectric behavior of the ceramics exhibited Debye-like relaxation, and could be explained based on a Maxwell–Wagner model. The activation energies calculated from the grain-boundary relaxation time constant were found to be in the range of 1.5–1.7 eV.