Impact of Gd3+ substitution on the structural, morphological, and electrical properties of lead-free Bi0.5Na0.5TiO3 ceramics

In the present work, we have reported the structural, morphological, dielectric, and electrical properties of the Gadolinium (Gd)-modified bismuth sodium titanate ceramic, i.e., (Bi1-xGdx)(0.5)Na0.5TiO3 (x = 0.00, 0.02, 0.04, and 0.06). This material was prepared via a mixed oxide solid-state method. Rietveld-refined XRD data and the Raman spectroscopy technique ratify the formation of the rhombohedral phase of the prepared compounds. The surface morphology of the material shows uniformly distributed and densely packed micrometer-sized grains. The dielectric constant substantially decreases with the substitution of Gd to pristine material. Complex impedance spectroscopic analysis confirms the non-Debye-type relaxation mechanisms in the compound. AC conductivity spectra of all the compounds are fitted nicely using the Jonscher power law. Nyquist plot describes the effect of grain and grain boundaries on resistivity of the material. A crossover from low frequency to high frequency, i.e., the shift from long-range hopping to short-range ionic mobility indicates the conductivity relaxation of the material (dispersion region). The increase in activation energy with increasing Gd concentration implies that when Gd ions enter the BNT's A-site, they reduce volatilization of Bi/Na ion.