Combustion Pressure Sensors using C-axis-oriented Aluminum Nitride Thin Films Prepared on Inconel Substrates

Abstract

C-axis-oriented aluminum nitride (AlN) thin films were prepared on Inconel substrates by the rf magnetron sputtering technique. The full-width at half-maximum (FWHM) of the X-ray rocking curve of the AlN films was 5.7°, and the piezoelectric constant d33 was 2.4 pC/N. The deviation from the linearity of charges with pressures for the AlN films were 0.2% of a full scale at 0.4 MPa, which indicated a good linearity. Furthermore the AlN films was evaluated under combustion pressures in a single-piston 90 cc engine rotating up to 4000 rpm. The waveforms of the AlN films were similar to those of a commercial sensor. It is demonstrated that the AlN films have a good possibility as combustion pressure sensor elements.