Combustion pressure sensors using C-axis-oriented aluminum nitride thin films prepared on Inconel substrates

C-axis-oriented aluminum nitride (AIN) 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 AIN films was 5.7 degrees, and the piezoelectric constant d(33) Was 2.4 pC/N. The deviation from the linearity of charges with pressures for the AIN films were 0.2% of a full scale at 0.4 MPa, which indicated a good linearity. Furthermore the AIN films was evaluated under combustion pressures in a single-piston 90 cc engine rotating up to 4000 rpm. The waveforms of the AIN films were similar to those of a commercial sensor. It is demonstrated that the AIN films have a good possibility as combustion pressure sensor elements.