Results in Physics (Dec 2019)
Development of tungsten doped Ni-Zn nano-ferrites with fast response and recovery time for hydrogen gas sensing application
Abstract
This paper reports on the study of series of tungsten doped Ni0.5Zn0.5WxFe2−xO4 (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) ferrites synthesized by a co-precipitation scheme. The crystallite size varies from 62 to 49 nm and the scanning electron microscope (SEM) images show the spinel cubic structure of the powder sample. Energy Dispersive X-ray Fluorescence Spectroscopy (EDXRF) confirms the presence of Ni, Zn, W and Fe elements in the prepared samples. The specific surface areas of the Ni0.5Zn0.5W0.2Fe1.8O4, Ni0.5Zn0.5W0.4Fe1.6O4 and Ni0.5Zn0.5W0.6Fe1.4O4 samples calculated from Brunauer-Emmett-Teller (BET) method are 18.9 m2/g, 21.5 m2/g and 24.6 m2/g, respectively. The metal oxide pellet type resistive sensor was made for gas sensor application. These sensors are selective for hydrogen (H2) gas. The performance of these sensors for sensing hydrogen gas at a concentration of 1000 ppm in the temperature range 80–300 °C has been investigated. Platinum electrodes were deposited on all the pellets by RF sputtering technique. The subsequent decomposition of platinum oxides on the metal oxide pellet surface results in an increase in surface roughness and electrical resistivity. The sensor shows a change in resistance from 1.21 × 105 Ω to 7.83 × 104 Ω in the presence of H2 gas even at alow temperature. The composition with x = 0.2 at an optimum temperature of 180 °C showed a fast response (14 s) and recovery time (20 s). High sensitivity, low cost, long term stability, high selectivity and fast response at low temperature makes this sensor useful for industrial applications. Keywords: Co-precipitation, Pellet type resistive sensor, Platinum decomposition, Hydrogen gas sensor, High selectivity, Low temperature, Sensitivity