D1.1 - High Temperature Stability of New Single Crystal Piezoelectric Sensors

SENSOR+TEST Conferences 2011
2011-06-07 - 2011-06-09
Proceedings SENSOR 2011
D1 - High Temperature Sensors I
C. Cavalloni, R. Sommer, M. Waser - Kistler Instrumente AG, Winterthur (Switzerland)
520 - 525


A new generation of high temperature sensors offering new perspectives in terms of performance and availability is in development. The sensors are based on superior synthetic monocrystalline piezoelectric materials. These crystals, known under the tradename PiezoStar®, have been well proved in numerous applications in harsh environments since many years. Among the outstanding properties of these crystals is their ability to perform continuously at temperatures above 600°C, the absence of pyroelectricity, great stability with no twinning and no phase transition up to the melting point (above 1300°C) as well as high sensitivity and mechanical strength. Other advantageous features for sensor applications are the favourable charge to capacitance ratio, the absence of ‘popcorn effects’ and very low thermal anisotropy. Furthermore, since they are artificially made the crystals are available in sufficient quantity and high quality.

The properties of the new crystal family provide an excellent basis for dynamic pressure sensors and accelerometers used in high temperature pplications such as humming detection in gas turbine combustors and vibration monitoring on hot structures. Special attention was paid to obtain high stability of the piezoelectric properties and to reduce vibration sensitivity of the pressure sensors. Examples of the new pressure and acceleration sensors designs are discussed and their performance at high temperature illustrated.

This paper examines the critical properties of PiezoStar® sensing elements for high temperature dynamic pressure sensors and accelerometers and compares them against known materials. The stability of the electrical insulation resistivity in different atmospheres has been investigated as function of temperature and time. In addition to the investigation of the PiezoStar® crystals several types of prototype sensors were built and initial tests conducted. Results available thus far indicate that PiezoStar® crystals are well suited for high temperature pressure sensors up to 600°C for continued operation and around 700°C for intermittent operation.