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A Measurement System to Determine the Electrical Properties of Piezoelectric Ceramics at High Temperatures
| Title: | A Measurement System to Determine the Electrical Properties of Piezoelectric Ceramics at High Temperatures |
| Author: | Gubinyi, Zoltan |
| Description: | Space exploration missions in the future will involve in-situ sampling and analysis under extreme environmental conditions, so these missions will require actuators and sensors that can operate reliably for a long period of time under these conditions. The commercially available sensors, actuators and motors cannot operate continuously at such a high ambient temperatures like +500°C, so this technical challenge requires new actuator and sensor designs. Piezoelectric materials with Curie temperature (TCurie) that is higher than +1000°C would be ideal for this role, but the commercially available piezoceramics only able operate reliably at low temperatures and very little information is available about their electrical properties at elevated temperatures. The original goal of this thesis was to develop a measurement system that is able to measure the properties of those high-temperature piezoelectric ceramics, La3Ga5SiO14 and La2Ti2O7 that are currently being developed at the NASA Glenn Research Center (GRC). However up to date; our attempts to polarize these high-temperature piezoelectric ceramics were unsuccessful. To be able to demonstrate the capabilities of the developed measurement system, commercially available Lead Zirconate Titanate (PZT) samples were used to measure the changes in the different vibration mode frequencies and electrical properties as the temperature was increased up to and above their Curie temperature, around +450°C. The developed measurement system was able to capture the changes as the operating temperature was increased to and above the Curie temperature of the materials. The description of the developed measurement system and the result of the measurements on a variety of piezoelectric materials are presented in this thesis. The PZT samples showed changes in the frequency range of their vibration modes and electrical properties as the temperature was getting closer to the TCurie, and in most cases these changes become very significant from around the TCurie-(50°C~20°C) temperature. The focus in this thesis was on the radial and thickness-extensional vibration modes. Based upon the measurements, there was a definite trend that difference between the anti-resonant and resonant frequencies of a vibration mode never increases with the temperature. This observation helped to predict the behavior of the coupling factors and the permittivity components of the materials as the temperature increased. However, to predict changes of the rest of the electrical properties turned out to be very difficult, since their behaviors depend on several factors, like the actual values of the resonant and anti-resonant frequency pairs and their relative changes to each other. This proves that to perform high temperature measurement is a reliable way to get information about the changes of the different vibration mode frequencies and electrical properties of the piezoelectric ceramics. This measurement system and the evaluation of measured data can be particularly useful to designers, because the collected information can help them to anticipate and incorporate the observed changes into their future actuator and sensor designs. |
| Permanent Link: |
http://rave.ohiolink.edu/etdc/view?acc_num=akron1145550983
http://hdl.handle.net/2374.OX/3718 |
| Date: | 2006 |
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