Ceramic thin film thermocouples for SiC-based ceramic matrix composites

Conductive ceramic thin film thermocouples were investigated for application to silicon carbide fiber reinforced silicon carbide ceramic matrix composite (SiC/SiC CMC) components. High temperature conductive oxides based on indium and zinc oxides were selected for testing to high temperatures in air. Sample oxide films were first sputtered-deposited on alumina substrates then on SiC/SiC CMC sample disks. Operational issues such as cold junction compensation to a 0 °C reference, resistivity and thermopower variations are discussed. Results show that zinc oxides have an extremely high resistance and thus increased complexity for use as a thermocouple, but thermocouples using indium oxides can achieve a strong, nearly linear response to high temperatures.

► Oxide thin film thermocouples tested for SiC/SiC ceramic matrix composites (CMCs)
► In2O3, N:In2O3, ZnO, AlZnO sputtered and tested on Al2O3 and CMC substrates
► ZnO, AlZnO have high resistance, complex temperature response.
► In2O3, N:In2O3 conductive at room temperature, more linear temperature response