Printed thermal sensors for harsh environment by plasma spray

Plasma spray is a versatile technology for coating dielectric, resistive and electrically conductive layers and therefore can be used for the printing of sensor devices. The printing of resistive thermal detectors (RTD) and thermocouples (TH) by plasma spray was investigated in order to generate robust thermal sensors able to withstand corrosive environment and high temperature, up to 900 °C. The thermal sensors have been deposited on steel plates and SiC rectangular tubes. The architecture of the RTD and thermocouples sensors is based on successive NiCr coating as a adhesion promoter, thick alumina or spinel dielectric coating, a NiCr/NiAl serpentine layers deposited via masking and a final alumina/spinel as encapsulating layer. The electrical properties versus temperature of the sensors are presented and discussed.