Ceramic Material
A ceramic oxide material with high fracture toughness and low thermal conductivity is used as a dielectric barrier and thermal insulation layer in sensor applications. In high temperature thin film gauges, yttria stabilized zirconia prevents electrical breakdown between the active grid and the metallic base. This material maintains its high mechanical strength at temperatures above one thousand degrees Celsius.
This ceramic layer has a high dielectric constant, which allows for effective electrical isolation with a thin film deposit.
Thermal Insulation
The addition of yttria stabilizes the cubic phase of zirconia, preventing the phase transitions that cause volume changes and cracking during heating. This stabilization is crucial for maintaining the structural integrity of the dielectric layer during thermal cycling. The material has a thermal expansion coefficient that matches closely with superalloys, reducing the thermal mismatch stress at the interface.
Deposition Quality
Sputter deposition parameters must be controlled to achieve the correct stoichiometry and density in the deposited film. Lower sputter rates are used to prevent the formation of defect structures that would reduce the dielectric strength of the ceramic. The cleanliness of the chamber during deposition determines the adhesion of the layer to the underlying metal.
Structural Verification
Diffraction testing is utilized to verify that the deposited film has achieved the stabilized cubic or tetragonal phase. This analysis ensures that the material will not undergo phase transformation during service, preventing delamination of the sensor stack. This verification completes the quality assurance process for high temperature ceramic coatings.
