Synthesis and Characterization of Mg Doped ZnBi2O6 (Zn1-xMg xBi 2O6 , x= 0.15 and 0.25) by Hydrothermal Method.

A comprehensive analysis of the electrical, optical, and dielectric properties of a material is essential for the research of device fabrication. From this perception, undoped ZnBi₂O₆ and magnesium (Mg) doped ZnBi₂O₆ (Zn_1-xMg _x Bi₂O₆ ) with a doping concentration x= 0.0, 0.15 & 0.25 have been synthesized using the hydrothermal method and then investigated to observe the optical absorbance, capacitance, and dielectric constant, etc. properties. The hydrothermal method is recognized as one of the best methods for the growth of crystalline structure because of some advantages like varieties of particle morphology, large-scale integration, and low-cost production with high crystallinity. We have used thermo-gravimetric analysis (TGA) to get the accurate guideline for phase formation temperature. The structural analysis was accomplished using X-ray diffraction (XRD) and scanning electron microscopy (SEM). From structural analysis, we observed a negative chemical pressure effect due to substituting lower ionic isovalent Mg 2+ to the higher ionic Zn ²⁺ on ZnBi₂O₆. Significant increments in unit cell volume and lattice parameters were observed with the increment of isovalent doping agent Mg ²⁺. This confirms the negative pressure effect for Mg²⁺ substitution on ZnBi₂O₆. It is expected that this salient finding will open a new window of research on ZnBi₂O₆. This will enable us in the future to control some transport and optical behavior of this promising material by adjusting suitable doping concentration according to our desired purposes. In this work, we have also calculated defect density, microstrain, grain size, and intensity ratio to observe the perfection of crystallinity. It was noticed that polycrystalline ZnBi₂O₆ and Zn_1-xMg _xBi ₂O ₆ (x= 0.15 & 0.25) were synthesized satisfactorily with minimum defects and lower impurity. This ensures the capability of the hydrothermal method to form higher-order crystallinity with greater perfection. Due to the negative chemical pressure effect, we also observed that the optical band gap of the synthesized samples increases with the increase of doping amount. The electrical resistivity was investigated using two probe methods. The optical properties of both doped and undoped samples were estimated using UV-Vis spectroscopy. The frequency-dependent electronic properties (conductance, dielectric constants, capacitance, impedance, reactance, resistance, and inductance) were investigated using a precision impedance analyzer. The obtained capacitances for all the samples were recorded in the Pico farad range with the lower value of dielectric constant throughout the high-frequency region.

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