Construction and Functionality of a Ceramic Resonant Pressure Sensor for Operation at Elevated Temperatures

• Main Authors: Matej Sadl, Andraz Bradesko, Darko Belavic, Andreja Bencan, Barbara Malic, Tadej Rojac
• Format: Article
• Language: English
• Published: MDPI AG 2018-05-01
• Series: Sensors
• Subjects: piezoelectric ceramic resonant pressure sensor; bismuth ferrite; high-temperature applications
• Online Access: http://www.mdpi.com/1424-8220/18/5/1423

Piezoelectric ceramic resonant pressure sensors have shown potential as sensing elements for harsh environments, such as elevated temperatures. For operating temperatures exceeding ~250 °C, conventional and widely used Pb(Zr,Ti)O3 (PZT) piezoelectrics should be replaced. Here, a ceramic pressure sensor from low-temperature co-fired ceramics (LTCC) was constructed by integrating a piezoelectric actuator made from bismuth ferrite (BiFeO3) on a diaphragm. This ferroelectric material was selected because of its high Curie temperature (TC = 825 °C) and as a lead-free piezoelectric extensively investigated for high-temperature applications. In order to construct a sensor with suitable pressure sensitivity, numerical simulations were used to define the optimum construction dimensions. The functionality of the pressure sensor was tested up to 201 °C. The measurements confirmed a pressure sensitivity, i.e., resonance frequency shift of the sensor per unit of pressure, of −8.7 Hz/kPa up to 171 °C. It was suggested that the main reason for the hindered operation at the elevated temperatures could lie in the thermo-mechanical properties of the diaphragm and the adhesive bonding at the actuator-diaphragm interconnection.