Nanocrystalline spinel [Ni.sub.x][Cu.sub.0.8-x] [Zn.sub.0.2][Fe.sub.2][O.sub.4]: a novel material for humidity sensing

The humidity sensing property of the ferrite systems [Ni.sub.x][Cu.sub.0.8-x][Zn.sub.0.2][Fe.sub.2][O.sub.4] with 0.0 ≤ x ≤ 0.8 (x = 0, 0.2, 0.4, 0.6, 0.8) was studied using the standard ceramic technique. The spinel structure of the compounds was confirmed by X-ray diffraction studies, BET study and surface morphology by scanning electron microscopy. The compounds were subjected to dc electrical conductivity studies at room temperature. The resistance measurements as a function of relative humidity (RH) in the range of 5-98% were done and the humidity sensing factors ([S.sub.f] = [R.sub.5%]/[R.sub.95%]) were calculated. The composite NiCuZn3 (x = 0.4) possessed the highest humidity sensing factor of 3051.9 ± 500, whilst CuZn-1 (x = 0) possessed the lowest humidity sensing factor of 45.3 ± 12. The other compounds possessed lower humidity sensing factors of 116.7 ± 35, 783.4 ± 160 and 416.2 ± 65 for x = 0.2, 0.6 and 0.8, respectively.