Structural and dielectric properties of Cerium doped Magnesium-Zinc Aluminate spinel nano-crystallites for high frequency applications

The Ce³⁺ doped Mg–Zn Aluminate spinel nano size crystals with compositional formula of Mg_0.5Zn_0.5Ce_xAl_2-xO₄ (x = 0.00, 0.02, 0.04, 0.06, 0.08 and 0.10) were synthesized by sol gel auto-combustion method followed by annealing at 800 °C for 3 h. The X-ray diffractometric (XRD) analysis confirmed space group FD3m and spinel structure of Ce³⁺ doped Mg–Zn Aluminates with crystallite size between 10 and 28 nm. Generally, an increasing trend in particles size and other structural parameters were observed at higher concentration of Ce³⁺ content. Transmission Electron Microscopy (TEM) was utilized to study the morphology and size of the Ce doped MG-Zn Aluminates that were consistent with XRD results. Furrier transforms infrared spectroscopy (FTIR) has been employed to reveal the absorption bands for the octahedral and tetrahedral sides observed in between 400 and 1000 cm⁻¹. All samples were pelletized to study the dielectric properties like dielectric constant, impedance, electric modulus and tangent loss. Impedance spectroscopy was employed at room temperature in the applied frequency ranging from 1 MHz to 3 GHz. A consistent behavior in dielectric constant and dielectric loss was observed for the intermediate range of applied frequencies. The concentration at x = 0.10 was found to exhibit the most stable dielectric constant and dielectric loss behavior at high frequencies. The effect of doping concentration on grain and grain boundaries, the polarization phenomena and conductivity mechanism has been discussed. It is found that AC conductivity for all doping concentration is low at lower frequencies range from 1 MHz to 300 MHz while a peak is observed at higher frequency around 2.5 GHz. The valuable responses of dielectric constant and dielectric lost at higher frequency range show that Mg_0.5Zn_0.5Ce_xAl_2-xO₄ can be used in high frequency devices.