Abstract
The highly crystallized orthoferrite of formula Nd0.5Ba0.5FeO3 (NBFO) was synthesized by the sol-gel method. The phase of our compound and the average particle size were studied using X-ray diffraction (XRD) and scanning electron microscopy (SEM) methods. The X-ray diffraction patterns showed that the NBFO sample crystallize in the cubic structure with Pm-3 m space group. The average crystallite size value determined by Williamson-Hall (W-H), Halder-Wagner (H-W) formula and using the method of Debye-Scherer is in the range of 60 nm, 56 nm and 55 nm, respectively. In the other hand, SEM result shows an overall average particle size of about 251 nm. Obviously, the particle sizes observed by SEM are larger than those calculated by XRD, which indicates that each particle observed by SEM consists of several crystallized grains. Moreover, the antiferromagnetic (AFM)-paramagnetic (PM) phase transition has been confirmed by magnetic measurements at 0.05 T applied field. This AFM-PM transition has been observed for the Neel temperature T-N = 49 K. Frequency and temperature dependencies of capacitance (C-f/T) and conductance (G-f/T) of the sample were investigated in the frequency and temperature ranges of 40 Hz-100 MHz and 220-400 K, respectively. On the other hand, the optical characteristics of this polycrystalline were analyzed by UV-Vis absorption spectroscopy. By investigating the UV absorption and reflectance measurements, we identify the direct optical band gap close to 4.75 eV, which confirms that our sample is a direct gap semiconductor. In addition, the Urbach energy, the optical extinction coefficient and the refractive index were determined from the absorbance and reflectance measurements. We have also shown that the refractive index n follows the Cauchy law in the area where the absorbance is maximized. On the other hand, the dispersion parameters E-0 and E-d of this compound have been calculated based to the Wemple-Didomenico model. Dielectric investigation indicates that the dissipation factor tan delta has a very low value.