Thermodegradation Effects in Thick-film Elements Based on Spinel Ceramic of Cu- and Co-enriched Compositions

: pp. 132 - 135
Lviv Politechnic National University

The modern state-of-the-art and perspectives to resolve the problem on negative temperature coefficient thermistor element for sensor electronics were analyzed. It was shown that thick-film technology in application to mixed transition-metal oximanganite ceramics is one of the most effective ways to achieve the final purpose — the elaboration of wide range of thermistors with high stability of their exploitation properties. The experimental investigation of kinetic dependences of thermally induced drift of electrical resistance in thick-films thermistor elements based on spinel-type ceramics of two compositions: Cu0.1Ni0.1Co1.6Mn1.2O4 (Coenriched) and Cu0.8Ni0.1Co0.2Mn1.9O4 (Cu-enriched) are performed. The thermal «shock» effect revealed itself in sharp increase of electrical resistance in Cu-enriched thick films on the initial stage of isothermal exposure at 170 oC with subsequent keeping of this value in the degradation test is observed. On the contrary, the smooth decrease in electrical resistance is disclosed in Co-enriched thick films in the process of their thermal degradation. It is established that electrical properties of Cu-enriched thick films can be stabilized owing to their isothermal exposure at relatively low temperatures. Their degradation kinetics are adequately described by the extended exponential-power-like relaxation function. This treatment procedure can be successfully used in order to obtain the high- stabile thick-film thermistor elements for sensor electronics.

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