Electrical properties of nickel-zirconia cermet films for temperature- and flow-sensor applications

Low-resistance Ni-ZrO2 cermet thin films with 30-78 vol.% Ni have been produced from metallo-organic deposition (MOD) precursor solutions. The films are spin coated onto Si or fused silica substrates and heat treated at 800-1100 degrees C for 1 h in forming gas (10% H-2/N-2) to reduce Ni, resulting in Ni and ZrO2 dispersions. Based upon the linearity of the temperature coefficient of resistance (TCR) and the magnetic susceptibility data, the optimum condition for sintering of 1 mu m thick Ni-ZrO2 cermet films is determined to be 800-900 degrees C in forming gas. The magnetic response of these cermets, and their increased resistance compared to NiFe-based alloys, make them suitable for use in magnetoresistive sensors. The objective in this work is to develop controlled Ni-ZrO2 thin-film structures for potential temperature-and flow-sensor applications. Predominantly metallic conduction is obtained on both Si and fused SiO2 substrates in 1 mu m thick cermet films with Ni content as low as 30 vol.%. TCR values of 3000-6800 ppm degrees C-1 are obtained for films with room-temperature resistances in the range 4-250 Omega/box. These films readily self heat, are strongly sensitive to air flow, with low power requirements of < 1 W and exhibit little hysteresis in flow response. (C) 1997 Elsevier Science S.A.