A smart-structure system can be defined as a system that can sense the external stimulus and respond to that stimulus quickly through a control system. Unique features of these systems will provide innovative capabilities and improvements in future aeronautics and space vehicle systems. NASA has been interested in piezoelectric materials as actuators and sensors for vibration control, shape control of aeronautical structures, noise reduction, adaptive flow control, and active combustion control. One emerging need is for high-temperature piezoelectric materials that function above 200 °C. There are techniques to measure the dielectric properties of piezoceramic materials to determine the Curie point. However, there are no existing test capabilities for measuring piezoelectric coupling coefficients at high temperatures. To assess the high-temperature performance of piezoelectric materials, researchers at the NASA Glenn Research Center designed and fabricated an experimental apparatus to measure piezoelectric properties. We also developed a benchmark test procedure using resonant analysis that is not addressed in an IEEE standard, and we measured the piezoelectric properties of a commercial lead zirconate titanate (PZT) piezoelectric disc as a function of temperature.
Absolute impedance Z versus frequency for Pb(ZrxTi1-x)O3-δ (Navy Type II; Pb, lead; Zr, zirconium; Ti, titanium; O, oxygen). All communication and control programs between the computer and its peripherals were written in the LabVIEW 7.1 language. The controller receives the temperature setpoints from the personal computer using the iTools program (Object Linking and Embedding for Process Control) server option. The frequencies were detected by a network analyzer within the frequency range of 10 kHz to 10 MHz.
The elastic properties CijklE piezoelectric coefficients ekij and εkS dielectric properties, and electromechanical coupling factors were determined as a function of temperature. These coefficients of the constitutive equations define the operating envelope in a temperature and frequency paradigm for radial and thickness mode vibrations. The graph above shows the location of resonant and antiresonant frequencies for PZT at room temperature. The measured resonant fs and antiresonant frequency fp pairs correspond to different vibration modes, fpr(1), fsr(1), fpr(2), fsr(2), fpt(1), fst(1), where the superscript r(i) refers to the first and second (i = 1, 2) resonant frequencies of the radial mode and the superscript t(1) refers to the first thickness mode resonant frequency.
A representative spectrum for the shifts in resonant frequencies as a function of temperature is shown in the next graph. The trend between antiresonant and resonant frequencies of a vibration mode with temperature helps to predict the behavior of the coupling factors and permittivity. The temperature-dependent piezoelectric coefficient d33 decreased with temperature. The coupling factor k33 was found to be relatively constant to 200 °C and to exhibit slight temperature dependence above 200 °C. The temperature sensitivity for both the piezoelectric coefficient and the electromechanical coupling factor were very small; the slopes Δd31T/d31T and Δk33/k33 were found to be 0.01 and -0.07, respectively, in the range of 120 to 200 °C.
First radial mode frequency shift with respect to temperature for Pb(ZrxTi1-x)O3-δ (Navy Type II). The resonance frequency shift was measured at 4 °C increments for a wide range of Pb(ZrxTi1-x)O3-δ samples that were engineered at the morphotropic phase boundary.
Planar coupling factor, kp, effective coupling factor, keff, and thickness-extensional mode coupling factor k33t, determined using a combination of Newton’s Law, constitutive equations, and Maxwell equations, as a function of temperature.
Thickness extensional mode piezoelectric constant, d33t and extensional mode piezoelectric constant, d31, as a function of temperature.
Glenn researchers developed a high-temperature measurement system to measure piezoelectric properties. In the present investigation, commercial PZT ceramics were examined under weak alternating electric fields. Then, an exact temperature use of these materials could be estimated by the current measurement system. This technique will organize and populate databases that describe the piezoelectric properties and facilitate the assessment of new piezoelectric materials that are currently being developed for higher temperature applications.
Case Western Reserve University contact: Dr. Ali Sayir, 216–433–6254, Ali.Sayir-1@ nasa.gov
Glenn contact:
Dr. Frederick W. Dynys, 216–433–2404, Frederick.W.Dynys@nasa.gov
Authors:
Dr. Ali Sayir, Dr. Frederick W. Dynys, Zoltan Gubinyi, and Dr. Celal Batur
Headquarters program office:
Aeronautics Fundamentals
Programs/projects:
Subsonic Fixed Wing
Last updated: December 14, 2007
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