Solution processed Mg+2:LaNiO3 thin films for effective methanol sensing

- Nominal composition of phase pure LaNiO3 and Mg+2:LaNiO3 thin films were synthesized by wet chemical route.
- Mg+2:LaNiO3 films are suitable for methanol sensing, the performance depends on the concentration of Mg+2 in the lattice.
- The selectivity with respect to other VOCs and effect of humidity were studied.

In this report the suitability and efficiency of methanol detection by solution processed LaxMg1-xNiO3 (x = 0.90, 0.75, 0.50) and LaMgxNi1-xO3 (x = 0.10, 0.25, 0.50) thin films are discussed. These films were deposited on silicon (110) substrates via spin coating techniques and annealed at 700 °C for 10 h in air. X-ray diffraction pattern of the films revealed pure phase rhombohedral perovskite type structure except for LaMg0.50Ni0.50O3 film where nickel oxide (NiO) and Lanthanum oxide (La2O3) phases were also observed. It was noticed that the response to methanol increased with temperature up to 300 °C, and then remained constant till ∼425 °C, peaking slightly at 300-325 °C. At this optimized temperature, the sensing performance could further be enhanced appreciably by increasing the molar concentration of Mg+2. So, at a set temperature of ∼325 °C, it was found that the sensing response of the films to methanol varied in the following sequence: LaMg0.50Ni0.50O3 > La0.50Mg0.50NiO3 > LaMg0.25Ni0.75O3 > La0.75Mg0.25NiO3 > LaMg0.10Ni0.90O3 > La0.90Mg0.10NiO3 > LaNiO3. Similar trends were observed for other volatile organic compounds (VOCs) such as acetone, ethanol, toluene and gases, such as CO2, CH4 and H2. It was found that the responses to VOCs and other gases were not affected by the relative humidity level (%) in the ambience. The methanol and acetone responses of the Mg+2:LaNiO3 films were also compared with those of solution processed La0.95Cu0.05NiO3 and La0.95Mg0.05FeO3 films.

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