Temperature-dependent dielectric and LPG sensing performance of millet extract-mediated combustion-engineered MgAl₂O₄ spinel nanoparticles

Magnesium aluminate spinel (MAS) nanoparticles were synthesized using diverse types of millets such as Kodo millet, Little millet, and Pearl millet extracts mediated combustion-engineered method. The XRD pattern shows crystalline nature and varying crystallite size. Morphological studies were done by scanning electron microscopy (SEM) and the weight percentage of magnesium, aluminum, and oxygen ions in the prepared samples was obtained from EDAX spectra. The peaks observed in the FTIR spectra confirm the bond formation of MgAl₂O₄ in the spinel structure. The observed absorbance peaks in UV–visible spectra and the band gap energy for all the prepared samples were found to be 6.41 eV. Frequency-dependent dielectric constant and dielectric loss of the samples in the range 100 Hz to 5 MHz at room temperature and in the temperature range from 100 to 800 °C are studied. Gas sensing response of MgAl₂O₄ nanoparticles was conducted at room temperature for different types of hydrocarbon gases like ethane, liquefied petroleum gas (LPG), butane, pentane, and methane and for flammable gases like ammonia and hydrogen sulfide at 500 PPB concentration. Response and recovery times for all the samples were noted. The results obtained show that the prepared samples may be suitable for high-frequency electronic, energy storage device applications, and for the detection of LPG in low concentration.