Effect of A-Site Pr-Doping on Dielectric and Thermoelectric Properties of Lanthanum Based La2FeNbO6 Double Perovskite Oxide Materials

Present study shows the structural, dielectric, and thermoelectric behaviors of Pr-doped La2FeNbO6 double perovskite oxide. The compound was synthesized via sol-gel technique followed by the sintering at 1473 K for 6 h in open air. XRD analysis reveals the observed pattern of La2-xPrxFeNbO6 [LPFNO] shows single phase cubic structure with Fm-3m space group and crystallite sizes were in similar fashion with morphological observation. Analysis of SEM images signifies the uniform distribution of grains in entire surface of the samples. The Maxwell-Wagner model has been used to explain the nature of the frequency-dependence dielectric constant of Pr-doped La2FeNbO6 Double Perovskite. The material undergoes a ferroelectric-para-electric phase transition, represented by a dielectric anomaly in its temperature-dependent dielectric permittivity investigation. At higher sintering temperatures, the investigation of Nyquist plots reveals the presence of nano-grains and grain boundary effects resulting from a conglomerate of nano-particles. The material’s conductivity follows Jonscher’s Power law and aligns with the large overlapping polaron tunneling model. The activation energy, akin to the energy needed for electron hopping, is determined using the Arrhenius equation. The sample exhibits negative temperature coefficient of resistance (NTCR) characteristics, indicating semiconductor behavior with temperature variation, according to impedance and conductivity analyses. Increasing Pr-content in LPFNO enhances dc-conductivity, power factor, and ZT up to certain high temperatures, indicating nearest neighbor hopping charge carrier conduction, followed by a rapid decline, signaling a transition to metallic-like behavior. Positive S throughout the examined temperature range suggests the presence of p-type charge carriers, while intrinsic behavior remains consistent with increasing Pr-content. Thermal conductivity decreases with rising temperature, suggesting dominant phonon-phonon (anharmonic) scattering. Such double perovskites are valuable for designing modern electronic devices, especially energy storage devices.