MATERIALS FOR HIGH-TEMPERATURE ACOUSTIC AND VIBRATION SENSORS - A REVIEW

The industrial and scientific communities have expressed a real need for the capability of pressure, acoustic, and vibration sensing at elevated temperatures. This review compares the various commercial methods and materials for acoustic transduction, identifying their advantages and limitations. Techniques and devices include simple piezoelectric sensors, accelerometers, strain gauges, proximity sensors, fiber optics and buffer rods. Sensors with operating temperatures in excess of 650-degrees-C are readily available from commercial sources. Of the mechanisms investigated, the piezoelectric approach offers several advantages, including design cost and simplicity. Therefore, the bulk of this review concentrates on piezoelectric materials, both those that are already available commercially, and those that are presently under development. The new materials include perovskite layer structure ferroelectric ceramics, which possess the highest known Curie temperatures, and thin film AlN, which has been reported to be piezoactive at 1150-degrees-C