Studies on sol–gel autocombustion processed Ni–Zn–Mg ferrite system: effect of calcination temperature, thermoelectric power, and gas sensing application.

Ni–Zn–Mg ferrites having the chemical composition Ni_0.7-xZn_xMg_0.3Fe₂O₄ (x = 0.1, 0.2, 0.3, 0.4, 0.5) were synthesized using easy and low cost-effective sol–gel autocombustion method. Thermogravimetric and differential thermal analysis (TGA–DTA), X-ray diffraction (XRD), Scanning electron microscopy (SEM), and Transmission electron microscopy (TEM) characterization techniques were used to characterize the synthesized samples. Structural and morphological properties of samples calcined at 500 °C, 600 °C, and 700 °C for 8 h were studied from XRD analysis and SEM analysis. Pure cubic phase along with proper grain growth was observed at calcined temperature 700 °C for 8 h. From TEM study of Ni_0.4Zn_0.3Mg_0.3Fe₂O₄ average grain size is observed to be in range 50–55 nm that revealed the formation of nanosized particles. Thermoelectric power measurement (TEP) shows the p-type behavior at low temperature and n-type behavior at high temperature. p–n transition temperature for Ni–Zn–Mg ferrite system under investigation lies in the temperature range 90–135 °C. Gas sensing properties of Ni–Zn–Mg ferrite thick films toward NO₂ and NH₃ gases revealed Ni_0.6Zn_0.1Mg_0.3Fe₂O₄ ferrite thick film shows good response along with quick response and recovery time as compared to other compositions under investigation. [ABSTRACT FROM AUTHOR]