Enhanced ammonia gas sensing properties of the ZnFe2O4 nanoparticles synthesized by wet chemical method

In the present work, zinc ferrite (ZnFe2O4) nanoparticles (NPs) were synthesized using a simple and economical wet chemical route, and the samples were calcined at three different calcination temperatures (600 degrees C, 700 degrees C, and 800 degrees C). The enhanced crystallite size of 59 nm for the ZnFe2O4 NPs calcined at 800 degrees C was confirmed using the XRD spectra. The surface morphology of the prepared samples exhibits homogeneous, irregularly shaped grains. Using the EDX examination, the existence of chemical constituents such as oxygen (O), zinc (Zn), and iron (Fe) was verified and, in addition, it was verified that the ZnFe2O4 NPs calcined at 800 degrees C contain no elemental impurities. The optical studies revealed a lower reflectance, higher absorption, and lowest bandgap value of 1.99 eV for the ZnFe2O4 NPs calcined at 800 degrees C. The VSM analysis showed that the ZnFe2O4 NPs possess a paramagnetic nature with improved saturation magnetization (M-s) of 4.71 x 10(-3) emu/g and coercivity (O-e) of 19, respectively, for the ZnFe2O4 NPs calcined at 800 degrees C. Finally, the gas sensing results showed that the fabricated ZnFe2O4 NPs calcined at 800 degrees C based sensors achieved a higher selectivity towards ammonia (NH3) at 25 ppm room temperature over other test gases, maximum response (134% at 150 ppm) with fast response and recovery time of 7 s and 7 s, minimum detectability of 72 ppb, better stability over 50 days, and good repeatability after 15 cycles, respectively. Also, the gas sensing response changes minimally at 74% humidity but improves significantly at 101% and 157%, likely due to increased water adsorption at oxygen vacancy sites indicating the better suitability of the sample for commercial gas sensing applications.