Material Composition
A thin layer of alloyed platinum and tungsten provides a stable resistive medium for high-temperature sensing applications. Utilizing platinum tungsten films offers a compromise between the high oxidation resistance of noble metals and the structural stability of refractory metals. These films typically function as the active element in strain gauges or pressure transducers.
Temperature Coefficient
Adding tungsten to the platinum lattice increases the electrical resistivity while lowering the temperature coefficient of resistance. This adjustment makes the sensor less sensitive to thermal fluctuations, which simplifies the electronic compensation required for accurate measurements. The specific alloy ratio determines the balance between sensitivity and stability.
Deposition Process
Sputtering techniques are used to deposit these films onto ceramic or silicon substrates with precise control over thickness and composition. Post-deposition annealing is a common step to stabilize the crystal structure and reduce internal stresses that could cause drift. If the film is not properly annealed, the resistance may change unpredictably during the first few cycles of high-temperature operation.
Quality control involves measuring the sheet resistance and checking the adhesion of the film to the underlying substrate using standardized scratch or peel tests.
Application Range
These alloys are chosen for environments where standard nickel or chromium films would oxidize or fail. Their high melting point and chemical inertness allow for reliable performance in harsh industrial exhaust streams.
