Effect of La3+ doping on structural, magnetic and LPG gas-sensing properties of Mg-Zn nano-ferrites

Abstract

A series of polycrystalline mixed spinel ferrites, Mg0.5Zn0.5LaxFe2-xO4 (x = 0, 0.025, 0.05, 0.075, 0.1) were synthesized by hydrothermal method, where NaBH4 was a reductant. The Rietveld refinement analysis demonstrated the La3+ occupancy in A and B positions. FESEM and HRTEM have shown nearly spherical nanoparticles with an average size of 7 nm. The existence of all the component elements were confirmed by EDS and XPS studies. Raman analysis have shown slight blue shift with higher La3+ concentration. These nano-ferrites were noticed to behave ferromagnetically, with small remanent magnetization. The nano-ferrites were tested for the LPG sensing, where the sensor response was understood by proposing the charge carrier (Fe2+ and Fe3+) hopping mechanism. The sensor response (%) of the sample (x = 5%) at 500 ppm exhibited highest value similar to 36, as compared to sample (x = 0%). To conclude, Mg0.5Zn0.5La0.05Fe1.95O4 showed better response and recovery time, rather than other spinel ferrites.