Novel Method for NTC Thermistor Production by Aerosol Co-Deposition and Combined Sintering

Abstract

A novel three-stage process to produce NTCR sensors is presented. In this process, an uncalcined powder mixture of NiO and Mn2O3 was deposited onto an alumina substrate via aerosol co-deposition (AcD). Then, an electrode structure was screen-printed onto the surface and the composite film was sintered in a multifunctional temperature treatment. Thereby, the sintering of the electrode, the formation of the NiMn2O4 spinel and the removal of film strains took place simultaneously. This enabled a significant reduction in energy demand and workload. The manufactured sensors, both as first prototypes, as well as miniaturized chip components, were characterized by a single-phase cubic NiMn2O4 spinel structure, mechanical stability and electrical properties that were similar to those of classical NiMn2O4 bulk ceramics or tempered aerosol deposited (AD) NiMn2O4 films. Particularly noteworthy was the high reproducibility and low variation of the NTCR parameters, such as the specific resistivity at 25 °C ρ25, the electrical resistance at 25 °C R25 and the thermistor constant B. The NTCR parameters were as aging-stable as for NiMn2O4 bulk ceramics or tempered NiMn2O4 AD-films and could even be further improved by thermal post-treatment.