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1Materials Research Institute, Pennsylvania State University, University Park, ... of Mechanical and Aerospace Engineering, North Carolina State University, ...
APPLIED PHYSICS LETTERS 96, 013506 共2010兲

Piezoelectric accelerometers for ultrahigh temperature application Shujun Zhang,1,a兲 Xiaoning Jiang,2,3 Michael Lapsley,2,4 Paul Moses,1 and Thomas R. Shrout1 1

Materials Research Institute, Pennsylvania State University, University Park, Pennsylvania 16802, USA TRS Technologies Inc., 2820 East College Ave., State College, Pennsylvania 16801, USA 3 Department of Mechanical and Aerospace Engineering, North Carolina State University, Raleigh, North Carolina 27695, USA 4 Department of Engineering Science and Mechanics, Pennsylvania State University, University Park, Pennsylvania 16802, USA 2

共Received 25 November 2009; accepted 16 December 2009; published online 6 January 2010兲 High temperature sensors are of major importance to aerospace and energy related industries. In this letter, a high temperature monolithic compression-mode piezoelectric accelerometer was fabricated using YCa4O共BO3兲3 共YCOB兲 single crystals. The performance of the sensor was tested as function of temperature up to 1000 ° C and over a frequency range of 100–600 Hz. The accelerometer prototype was found to possess sensitivity of 2.4⫾ 0.4 pC/ g, across the measured temperature and frequency range, indicating a low temperature coefficient. Furthermore, the sensor exhibited good stability over an extended dwell time at 900 ° C, demonstrating that YCOB piezoelectric accelerometers are promising candidates for high temperature sensing applications. © 2010 American Institute of Physics. 关doi:10.1063/1.3290251兴 High temperature sensors are widely used and sought after in aerospace, automotive, energy generation, and other systems. For example, high temperature sensors have been identified as one of the critical technologies that will enable safer, more fuel efficient, and more reliable vehicles for aeronautics and space transportation. Industrial applications of high temperature sensors exist in engine health monitoring for both turbine and piston engines, in which the sensors must be able to operate reliably under the harsh internal environments of an engine, when the sensors often need to be as close as possible to the engine component of interest for adequate sensitivity.1–3 Extensive effort has been expended to develop high temperature sensors including thermocouples, platinum 共Pt兲 strain gages, microelectromechanical system 共MEMS兲, silicon carbide 共SiC兲 sensors, and fiber optic sensors. However, they suffer from low sensitivity, short lifetimes, limited operational temperature ranges 共⬍700 ° C兲 and/or complex packaging.1,4–6 Piezoelectric sensors for high temperature applications have attracted significant attention, offering relatively simple structures, fast response times, and easy integration.7–10 Accelerometers based on piezoelectric materials are of interest for measuring and recording dynamic mechanical parameters including shock, stress, and vibration. Most existing piezoelectric accelerometers are made of quartz crystals, piezoelectric ceramics 共e.g., lead zirconic titanate or lead metaniobate兲, and, for higher temperature operation 共⬎500 ° C兲, single crystal tourmaline or langasite.11–13 More recently, gallium phosphate 共GaPO4兲 piezoelectric crystals have been proposed as a candidate for high temperature sensing applications to 900 ° C.14,15 However, the use of the above materials at elevated temperature often presents challenges in addition to the simple change in electromechanical properties according to a predictable temperature coefficient. Those challenges include: material phase transitions, which lead to large variaa兲

Author to whom correspondence should be addressed. Electronic mail: [email protected].

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tions in the electromechanical coefficients and can cause irreversible degradation of the material properties; increased electrical conductivity which interferes with the detection of the piezoelectrically induced charge; and increased attenuation of acoustic waves from mechanical loss. All of these factors must be considered when choosing the appropriate material for a particular high temperature application.16,17 Recently, crystals in the oxyborate family YCa4O共BO3兲3 共YCOB兲 have been reported to possess a piezoelectric d33 coefficient of 6.5 pC/N, three times that of quartz, with a d33 · g33 product, being on the order of 4.4 ⫻ 10−13 C Vm/ N2, comparable to GaPO4 crystals.19 The electrical resistivity of YCOB is on the order of 10 M⍀ cm at 1000 ° C, two to three orders of magnitude greater than langasite crystals.18,19 Furthermore, in contrast to quartz and GaPO4, no phase transition has been observed in YCOB crystals prior to its melting point 共1500 ° C兲.18–21 It is the purpose of this research to investigate YCOB crystals’ functionality for high temperature acceleration sensing applications, using an accelerometer prototype at temperatures up to 1000 ° C. All references to YCOB in this study refer to material with the 共XYlw兲-15° / 45° cut, which was used as the compression mode transduction element in the accelerometer. A single layer 共monolithic兲 was selected for the accelerometer fabrication, with crystal dimensions of 15⫻ 7 ⫻ 2 mm3, resulting in a capacitance of 5.1 pF, consistent with the reported dielectric permittivity of 11. The designed resonance frequency was approximately 1 MHz, well above the tested frequency range of the accelerometer. Figure 1 shows a schematic diagram of the monolithic compression-mode accelerometer assembly, in which 共2兲 is a seismic mass, whose inertial force under acceleration is measured by the piezoelectric YCOB crystal transduction element 共4兲. A screw 共7兲 passing through the preloading sleeve 共6兲 compresses the piezoelectric element 共4兲 between the seismic mass 共2兲 and the base plate 共1兲. Inconel was chosen as the mass material due to its high density 共⬎8.1 g / cc兲, and because its thermal ex-

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FIG. 2. Sensor charge as a function of acceleration at room temperature and elevated temperature of 900 ° C 共the small inset is the snapshot from Oscilloscope, showing the driving voltage and sensor voltage兲. FIG. 1. Schematic diagram of the monolithic compression mode accelerometer sensor assembly.

pansion coefficient 共⬃10 ppm/ K兲 is similar to that of YCOB 共⬃8 ppm/ K兲 and stainless steel 共10–12 ppm/K兲, the material used to fabricate the screw and the preloading sleeve. In the prototype assembly, 共3兲 is high purity alumina for electrical insulation and 共5兲, the top and bottom electrodes, are made of platinum foil 共50 ␮m in thickness兲 connected to shielded platinum leads, which are attached to a coaxial cable outside the furnace. The same platinum foil was also used as gasketing for the unevenness between the crystal surface 共4兲 and insulation 共3兲/seismic mass 共2兲, respectively. An electromagnetic vibration stage 共Model ES020, KCF Technologies兲 was used as the excitation source which provided up to 16 g of acceleration in the operational frequency. The sensor was positioned inside a vertical split-tube furnace and attached, via an alumina rod 共8兲, to the vibration stage, located beneath the furnace. The sensor was shielded to minimize environmental noise. An impedance gain-phase analyzer 共HP 4194A兲 produced a sinusoidal signal, sweeping across the required frequency range 共100–600 Hz兲. This signal was amplified by an audio amplifier 共Dual XPA2500兲 to drive the vibration stage, whose voltage was also recorded by the reference channel of the impedance analyzer and an oscilloscope 共Agilent Infiniium 54853A 2.5 GHz兲, using a compensated oscilloscope probe as a voltage divider. The charge developed in the YCOB piezoelectric crystal was converted to voltage by a charge converter and amplifier 共Model 422E12, PCB Piezotronics兲, whose output voltage was monitored on the test channel of the gain-phase analyzer. The time domain waveform of both the vibration stage and tested sensor were also recorded on the oscilloscope. In order to characterize the compression-mode vibration sensor, the signal output was recorded as a function of temperature 共room temperature to 1000 ° C兲, vibration frequency 共100–600Hz兲, vibration stage drive voltage 共acceleration兲 and high temperature dwell time 共at 900 ° C兲. Relatively low acceleration and vibration frequency were used because of mechanical resonance in the bulky fixture required for high

temperature testing. In addition, due to imperfect shielding of environmental noise 共heater power line兲 at 60 Hz, the lower test frequency limit was chosen to be 100 Hz, although measurements could also be obtained at 20 Hz, below the 60 Hz interference. Prior to measurements, the prototype sensor was calibrated at room temperature by comparing its performance with a commercial vibration sensor 共Model 357B03, PCB Piezotronics兲. Based on the calibration test and the conversion factor of the charge converter, the sensitivity of the prototype sensor was determined to be 2.3 pC/g, across the tested frequency range at room temperature. Figure 2 shows the generated charge as a function of acceleration measured at 600 Hz. The charge increased linearly with amplitude, both at room temperature and an elevated temperature of 900 ° C, giving a slope of 2.3 pC/g in both cases, though electrical interference caused more noise in the 900 ° C measurement. The inset in Fig. 2 gives a snapshot from the oscilloscope, showing the drive voltage to the vibration stage and the generated sensor voltage. Compared to the drive voltage, there is 180° phase shift in the sensor’s response due to the charge amplifier’s conversion hardware. Figure 3 shows the sensitivity of the accelerometer as a function of frequency and temperature. It was found that the monolithic compression mode accelerometer demonstrated a sensitivity of 2.4⫾ 0.4 pC/ g with little variation across the tested temperature and frequency range. In order to test the high temperature survivability and reliability, the sensor was held in the furnace at 900 ° C, for more than three hours 共time was limited to prevent heat damage to the vibration stage兲, and data was obtained every half hour during the test. Figure 4 summarizes the sensitivity as a function of dwell time at different frequencies, where the sensitivity was found to be 2.4⫾ 0.4 pC/ g at 900 ° C for more than 3 h. The variation of sensitivity with time was found to be minimal. In summary, a compression-mode accelerometer prototype based on piezoelectric single crystal YCOB was designed, fabricated, and tested as a function of temperature from room temperature to 1000 ° C over the frequency range of 100–600 Hz. The sensitivity of the accelerometer was found to be 2.4⫾ 0.4 pC/ g across the measured temperature

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YCOB crystal layers in the accelerometer offers clear potential for further improving the sensor performance. This work was supported by NASA under Grant No. NNX09CC63P. Program manager Mr. Larry Hudson is acknowledged for helpful discussions. The authors also wish to thank Mr. Matt Corbin, Mr. Dick Brenneman, and Ms. Hua Lei for the help in machining the prototype. 1

FIG. 3. Sensitivity of the compression mode accelerometer sensor as function of temperature up to 1000 ° C at different frequency range.

and frequency ranges. The high temperature dwell tests revealed stable behavior, thus demonstrating the potential of YCOB as a material for vibration sensing in an extreme environment, offering a high working temperature range 共up to at least 1000 ° C兲 with a low temperature coefficient, high temperature stability and moderate sensitivity. Given this prototype’s capacitance of only 5.1pF and YCOB’s d33 · g33 product of 4.4⫻ 10−13 C Vm/ N2, increasing the number of

FIG. 4. Sensitivity of the compression mode accelerometer sensor as function of dwell time at 900 ° C.

G. Hunter, J. Wrbanek, R. Okojie, P. Neudeck, G. Fralick, L. Chen, J. Xu, and G. Beheim, Proc. SPIE 6222, 622209 共2006兲. 2 T. R. Shrout, R. Eitel, and C. Randall, in Piezoelectric Materials in Devices, edited by N. Setter 共Ceramics Laboratory, EPFL, Lausanne, Switzerland, 2002兲, p. 413. 3 S. J. Zhang, J. Luo, D. W. Snyder, and T. R. Shrout, in Advanced Dielectric, Piezoelectric and Ferroelectric Materials-Synthesis, Characterization and Applications, edited by Z. G. Ye 共Woodhead, Cambridge, England, 2008兲, Chap. 5, p. 130. 4 R. S. Okojie, D. Lukco, L. Y. Chen, and D. J. Spry, J. Appl. Phys. 91, 6553 共2002兲. 5 C. S. Cho, G. C. Fralick, and H. D. Bhatt, J. Spacecr. Rockets 34, 792 共1997兲. 6 G. W. Hunter, P. G. Neudeck, J. Xu, D. Lukcol, A. Trunek, M. Artale, P. Lampard, D. Androjna, D. Makel, B. Ward, and C. C. Liu, Mater. Res. Soc. Symp. Proc. 815, J4.4.1 共2004兲. 7 V. Mortet, R. Peterson, K. Haenen, and M. D’Olieslaeger, Appl. Phys. Lett. 88, 133511 共2006兲. 8 S. Rhee, J. Suzuki, S. J. Zhang, and T. R. Shrout, Proceedings of the 12th US-Japan Seminar on Dielectric and Piezoelectric Ceramics, Maryland, US, 2005 共unpublished兲, p. 115. 9 Z. Wang, H. Zhu, Y. Dong, and G. Feng, Meas. Sci. Technol. 11, 1565 共2000兲. 10 K. Kishi, Y. Ooishi, H. Noma, E. Ushijima, N. Ueno, M. kiyama, and T. Tabaru, J. Eur. Ceram. Soc. 26, 3425 共2006兲. 11 M. N. Hamidon, V. Skarda, N. M. White, F. Krispel, P. Krempl, M. Binhack, and W. Buff, Sens. Actuators, A 123–124, 403 共2005兲. 12 S. J. Zhang, Y. Q. Zheng, H. K. Kong, J. Xin, E. Frantz, and T. R. Shrout, J. Appl. Phys. 105, 114107 共2009兲. 13 H. Fritze and H. L. Tuller, Appl. Phys. Lett. 78, 976 共2001兲. 14 P. Krempl, G. Schleinzer, and W. Wallnofer, Sens. Actuators, A 61, 361 共1997兲. 15 P. M. Worsch, P. W. Krempl, and W. Wallnofer, Proceedings of IEEE on Sensors, 2002, p. 589. 16 D. Damjanovic, Curr. Opin. Solid State Mater. Sci. 3, 469 共1998兲. 17 G. Gautschi, Piezoelectric sensorics 共Springer, New York, 2002兲. 18 S. J. Zhang, Y. T. Fei, B. H. T. Chai, E. Frantz, D. W. Snyder, X. N. Jiang, and T. R. Shrout, Appl. Phys. Lett. 92, 202905 共2008兲. 19 S. J. Zhang, Y. T. Fei, E. Frantz, D. W. Snyder, B. H. T. Chai, and T. R. Shrout, IEEE Trans. Ultrason. Ferroelectr. Freq. Control 55, 2703 共2008兲. 20 S. J. Zhang, E. Frantz, R. Xia, W. Everson, J. Randi, D. W. Snyder, and T. R. Shrout, J. Appl. Phys. 104, 084103 共2008兲. 21 T. Nishida and T. Shiosaki, Proceedings of IEEE on International Ultrasonics Ferroelectrics Frequency Control Joint 50th Anniversary conference, 2004, p. 1988.