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

Matej Sadl,Andraz Bradesko,Tadej Rojac,Barbara Malic,Darko Belavic,Andreja Bencan

doi:10.3390/s18051423

Abstract

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 ( = 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.

Highlights

Pressure sensors are required in a wide variety of applications and in different environments that cover a broad range of pressures spanning from below ~10−5 bar to above a few 100 bars
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
Pressure sensors have so far been constructed in different designs, the simplest and most commonly used is the edge clamped diaphragm, with integrated sensing elements for detection of its deflection caused by the applied pressure [1]

Summary

Introduction

Pressure sensors are required in a wide variety of applications and in different environments that cover a broad range of pressures spanning from below ~10−5 bar to above a few 100 bars. Not one sensor is universal and it is not possible to cover such a wide pressure range and the fulfill demands required for each specific application. The resonant pressure sensor operates by monitoring the shift of the diaphragm’s resonance frequency in relation to differential pressure. The frequency shift is proportional to the change of a differential pressure.

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