Structural, Magnetic, Optical and Dielectric Characteristics of Ba2− Z Y Z Mnteo6 (Y= La, Bi & Sr; Z = 0 & 0.1) Double Perovskite Oxides

Abstract

We report the structural, magnetic, I−V characteristics, optical and dielectric properties of polycrystalline Ba2−zYzMnTeO6 (Y = La, Bi, and Sr; and z = 0 and 0.1) double perovskite oxides. Cubic crystal structure with Fm3̅m space group symmetry was confirmed by the X-ray powder diffraction (XRD) analysis at the room temperature. By adding dopants (Sr2+, Bi3+, and La3+) to the Ba2MnTeO6 sample at the A-site, the lattice parameter increases by 10 %, going from 8.11 to 8.23 Å. Magnetic measurements indicated that all samples showed antiferromagnetic-type interactions except Ba1.9La0.1MnTeO6 sample. The Neel temperature (TN), Curie-Weiss constants (θCW) and effective magnetic moment (μeff) values range from (20−22 K), (−98 to −158 K) and (4.53−4.65 μB), respectively. Indirect and direct bandgap (B.G.) energies were estimated by the diffused reflectance spectroscopy (DRS) investigation. In addition, the I−V characteristics were examined throughout the temperature range of 25−900 ℃, and it is observed that as temperatures increased, all samples exhibited behavior ranging from insulating to semiconducting-type nature. The synthesized samples seem to be good for application in high-performance capacitors, given their high dielectric constant (∈∞) values between 6.01 and 12.67 and specific surface areas ranging from 13.34 to 17.33 m²/g. The relaxation phenomena, as shown by the Nyquist plot, is compatible with a model that is not Debye, and the relaxation times range from 1.937 to 133.690 × 105 s. The inspection of Cole-Cole plot semicircles proposes that conduction effects within the grains are prevailing in the Ba2MnTeO6 sample, while resistive grain boundary effect dominates in the Sr-, Bi- and La-doped Ba2MnTeO6 compounds.

Keywords: Double Perovskite, X-ray powder Diffraction, Antiferromagnetic, Neel temperature, Dielectric constant, Nyquist plot and Cole-Cole plot