Abstract
This paper examines the influence of a short-term thermal treatment of aerosol deposited negative temperature coefficient (NTC) thermistor films on the NTCR characteristics and their long-term stability with different electrode materials. An aerosol deposition of a spinel-based NiMn2O4 powder on alumina substrates with screen-printed AgPd and Au interdigital electrode structures was performed. The manufactured components of the typical size of 1206 were tempered in a moderate temperature range of 200 °C to 800 °C and aged for 1000 h at 125 °C in air. Based on R-T measurements in a high-precision silicone oil thermostat bath and high temperature XRD analyses, the influence of the thermal treatment was analyzed and discussed. A 60-min tempering at 400 °C proved to be optimal, as both the NTCR parameters and their ageing stability could be significantly improved. The findings are explained.
Highlights
Spinel-type nickel manganite Nix Mn3-x O4, such as NiMn2 O4 (x = 1) are semiconducting ceramics, the electrical resistance of which decreases approximately exponentially with increasing temperature
NTCR sensors are mainly bulk ceramics [10], which are produced in the form of chips, discs or SMD [11]
The fragmented and plastically deformed particles can be seen in the nanometer range in the aerosol-deposited NiMn2 O4 film
Summary
Spinel-type nickel manganite Nix Mn3-x O4 , such as NiMn2 O4 (x = 1) are semiconducting ceramics, the electrical resistance of which decreases approximately exponentially with increasing temperature (thermally sensitive resistor, thermistor [1]) Due to their high negative temperature coefficient (NTC), nickel manganites are a well-known and a widely used base materials class for ceramic NTC thermistors in industry [2,3]. NTCR sensors are mainly bulk ceramics [10], which are produced in the form of chips, discs or SMD [11] They are usually produced by traditional ceramic and sinter-based processes with controlled sintering profiles and temperatures above 1000 ◦ C [12]. Due to the poor sinterability of NTCR ceramics, problems such as porosity, lack of stability and reproducibility must be handled [10,13,14]
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