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

• Main Authors: Michaela Schubert, Christian Münch, Sophie Schuurman, Véronique Poulain, Jaroslaw Kita, Ralf Moos
• Format: Article
• Language: English
• Published: MDPI AG 2019-04-01
• Series: Sensors
• Subjects: aerosol deposition method (ADM), RTIC; NiMn₂O₄ ceramic; NTCR device; temperature sensor; thick film thermistor
• Online Access: https://www.mdpi.com/1424-8220/19/7/1632

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 <i>ρ</i>₂₅, the electrical resistance at 25 °C <i>R</i>₂₅ and the thermistor constant <i>B</i>. 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.