Microstructure, dielectric relaxation, optical, and ferroelectric studies of a lead-free double perovskite: BaLiFeMoO6

In this article, the influence of co-substitution of alkali and transition metals at the Ba/Mo site of host BaMoO4 (inorganic Scheelite) is reported. A new lead-free double perovskite BaLiFeMoO6 (BLFMO) is synthesized using a conventional solid-state reaction route, having tetragonal crystal symmetry with an average crystallite size of 93.2 nm and strain of 0.115%. Grains are grown by sintering and distributed uniformly through well-defined grain boundaries as obtained from scanning electron microscopy (SEM). The purity and compositional analysis through energy-dispersive analysis X-ray spectroscopy (EDX) technique confirms the presence of constituent elements Ba, Li, Fe, Mo, and O. Raman study supports the substitution of Li/Fe atoms at Ba and Mo sites in the host matrix. Direct bandgap energy of 2.99 eV is calibrated using the ultraviolet-visible (UV-Vis) spectrum; may be suitable for photovoltaic applications. Maxwell-Wagner dielectric response, non-Debye relaxation, activation energy, and negative temperature coefficient resistance (NTCR) behavior are the outcomes of the synthesized sample characterized using dielectric, impedance, modulus, and conductivity plots in a wider spectrum of frequency (1 kHz-1 MHz) and temperatures (25-500 & DEG;C). The contribution of both grains and grain boundaries in the conduction mechanism has been investigated using Nyquist's fitting data calibrated from ZSIMPWIN software. A decrease in the magnitude of grain boundary resistance with a rise in temperature in fitted Nyquist's plot suggests the presence of semiconducting nature in the material. Analysis of leakage current density suggests that the nature of the conduction mechanism follows to the space charge limited current process. The study of temperature-dependent resistance supports BLFMO as a good candidate for NTC thermistor-related device applications. The study of polarization-electric field hysteresis loop suggests the possibility of the ferroelectric nature in the studied sample.