APPLIED PHYSICS LETTERS 92, 202905 共2008兲
Characterization of piezoelectric single crystal YCa4O„BO3…3 for high temperature applications Shujun Zhang,1,a兲 Yiting Fei,2 Bruce H. T. Chai,2 Eric Frantz,3 David W. Snyder,3 Xiaoning Jiang,4 and Thomas R. Shrout1 1
Materials Research Institute, Pennsylvania State University, University Park, Pennsylvania 16802, USA Crystal Photonics Inc., 5525 Benchmark Lane, Sanford, Florida 32773, USA 3 Electro-Optics Center, Pennsylvania State University, Freeport, Pennsylvania 16229, USA 4 TRS Technologies, Inc., 2820 E. College Ave., State College, Pennsylvania 16801, USA 2
共Received 14 April 2008; accepted 4 May 2008; published online 22 May 2008兲 Operation at temperatures well above ambient is desired for applications such as smart structures integrated within aircraft and space vehicles. Piezoelectric yttrium calcium oxyborate single crystal YCa4O共BO3兲3 共YCOB兲 was found to exhibit no phase transition until its melting temperature around ⬃1500 ° C. The temperature characteristics of the resonance frequency, electromechanical coupling, and dielectric permittivity were studied in the temperature range of 30– 950 ° C for different orientations. The electrical resistivity at 800 ° C was found to be greater than 2 ⫻ 108 ⍀ cm. Together with its temperature independent electromechanical coupling factor 共⬃12% 兲 and engineered resonance frequency behavior, these make YCOB crystals excellent candidates for sensing applications at ultra high temperatures. © 2008 American Institute of Physics. 关DOI: 10.1063/1.2936276兴 High temperature electronics is an area of research offering advanced materials and design challenges and one of significant industrial importance.1,2 High temperature actuators for structural control and high temperature sensors for structural health monitoring would allow the development of lightweight composite aircraft that could operate with increased maneuverability and fuel efficiency. High temperature sensors for health monitoring of furnace components and reactor systems are also desirable in coal-fired electric generation plants and/or nuclear plants.3 Ferroelectric materials with high piezoelectric properties are the mainstay for actuating and sensing in smart structures, however, their poor performance at elevated temperatures is a barrier in many applications. For example, most perovskite ceramics possess Curie temperatures less than ⬃350 ° C 关e.g., Pb共Zr, Ti兲O3兴 and their piezoelectric properties deteriorate at less than half of their corresponding Curie temperatures.1,4,5 Bismuth-titanate compositions with perovskite layer structures exhibit Curie temperatures in the range of 500– 900 ° C, but their relatively low piezoelectric coefficient and electrical resistivity, limit their sensor application in the temperature range less than 500 ° C.4 Quartz 共SiO2兲 is one of the earliest piezoelectric crystals used in electronic devices, however, its usage range is normally limited to 艋350 ° C, above which the crystal structure is subject to twinning, destroying its piezoelectric property.1 Piezoelectric crystals of the langasite 共formally La3Ga5SiO14兲 and its isomorphs, such as langanite and langatite, to name a few, can be grown using the Czochralski method and have been actively investigated for surface acoustic wave applications.6–9 Langasite family crystals do not undergo phase transformations up to their melting temperatures around 1470 ° C, but their low resistivity at elevated temperatures limit their application range.4,5 Analogous to SiO2 quartz, gallium orthophosphate 共GaPO4兲 was reported to be grown using hydroa兲
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thermal method and was found to possess thermally stable piezoelectric properties up to 950 ° C, at which an irreversible transformation into a cristobalitelike phase occurs.4,5,10–12 However, unlike quartz, the hydrothermal growth of GaPO4 is very slow and costly. Oxyborate crystals ReCa4O共BO3兲3 共ReCOB兲 共Re= rare earth elements兲, including GdCOB, YCOB, and LaCOB can be readily grown from the melt using the Czochralski method.13,14 This family of crystals has been extensively studied for nonlinear optical and/or laser applications due to its large transparency range, reasonable nonlinear optic coefficient共s兲, and high damage threshold.15–18 The piezoelectric properties at room temperature for GdCOB and LaCOB crystals have been reported with piezoelectric coefficients and dielectric permittivity on the order of 2 – 9 pC/ N and 10–15, respectively, comparable to GaPO4 and langasite crystals.19–22 In this work, the temperature characteristics of the electrical resistivity, dielectric, piezoelectric resonance frequencies, and electromechanical properties for YCOB piezoelectric single crystals were studied in detail. The YCOB crystal belongs to monoclinic structure with Cm space group, the relationship between crystallographic a, b, and c axes and crystallophysic X, Y, and Z axes was discussed in references 18 and 23 and given in the inset Fig. 1. The samples for electrical measurements were 共ZYwt兲 − , 共0 ° 艋 艋 90° , = 135° 兲 cut extensional bars. The samples were sputtered with platinum thin film on the parallel surfaces as the electrodes. The resistance was measured using a source meter 共Keithley 2410C兲 and the dielectric properties were determined using a multifrequency LCR meter 共HP 4284A兲. The piezoelectric coefficient was obtained from a Berlincourt type d33 meter. The resonance and antiresonance frequencies were obtained from impedancephase gain analyzer 共HP4194A兲. The effective electromechanical coupling and mechanical quality factors were calculated according to IEEE standards.24
0003-6951/2008/92共20兲/202905/3/$23.00 92, 202905-1 © 2008 American Institute of Physics Downloaded 23 May 2008 to 128.118.37.3. Redistribution subject to AIP license or copyright; see http://apl.aip.org/apl/copyright.jsp
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FIG. 2. Dielectric permittivity and dielectric loss as a function of temperature for different cut YCOB samples. FIG. 1. Electrical resistivity as a function of temperature for 共ZYwt兲40° / 135° oriented YCOB, the inset gives the relationship between crystallographic and crystallophysic axes 共after Ref. 23兲.
Room temperature dielectric and piezoelectric properties for YCOB crystals with different orientations are listed in Table I. The dielectric permittivity was found to be 9–11, depending on the different crystal cut. The dielectric loss and mechanical quality factors were found to be on the order of ⬍0.1% and ⬎10k, respectively. The piezoelectric coefficients d33 varied between 0 – 6.5 pC/ N, with the maxima value found for orientations of 共ZYwt兲 = 30° – 50°. It is worth pointing out that YCOB crystals exhibit very high piezoelectric voltage coefficients g33, in the range of 共10– 67兲 ⫻ 10−3 Vm/ N, two times higher than perovskite materials, primarily an aspect of its very low dielectric permittivity. The extensional effective electromechanical coupling factors were in the range of 1%–12%, with the highest value on the order of 11.9% for 共ZYwt兲 30°–40°/135°, decreased to lower value on the order of ⬃9% when the direction is rotated away. The resonance frequency constants were found to be in the range of 2600– 3000 Hz m. Figure 1 gives the electrical resistivity 共兲 values for YCOB crystal with orientation of 共ZYwt兲 40°/135° as a function of temperature, demonstrating that YCOB exhibits very high resistivity at elevated temperature, with value on the order of 2 ⫻ 108 ⍀ cm at 800 ° C, three orders higher than langasite crystal and one order higher than GaPO4 crystal, respectively, at the same temperature. The activation energy Ea calculated according to Arrhenius law was found to be on the order of 1.6 eV. Figure 2 presents the dielectric behavior as a function of temperature measured at a frequency of 100 kHz for different orientation cuts. The dielectric permittivity was found to
be on the order of 9–11 for different cuts at room temperature, increasing by ⬃20% at 950 ° C. The dielectric loss 共Fig. 2 inset兲 was found to be less than 0.1% at room temperature and remained ⬍30% at 950 ° C, exhibiting overall very stable dielectric behavior. No more data was obtained over 950 ° C owing to the degradation of platinum thin film electrodes. The piezoelectric coefficient d33, dielectric permittivity, and dielectric loss were found to maintain the same values at room temperature after annealing YCOB samples up to 1400 ° C, indicating that no phase transformation occurs prior to its melting temperature. The extensional mode resonance 共f r兲 and antiresonance frequency 共f a兲 characteristics of the impedance and phase at room temperature are shown in Fig. 3, from which the effective extensional coupling factor keff was calculated to be on the order of ⬃11.9% for 共ZYwt兲40° / 135°, with a mechanical quality factor Q on the order of ⬎11 000. Of particular interest for YCOB crystals is their high temperature electromechanical behavior. As can be observed from the inset in Fig. 3, the impedance and phase characteristics at 900 ° C, the phase maximum was found to be on the order of 88°, indicative of very low loss at this temperature and correspondingly, the mechanical Q value was calculated to be ⬎5000. Temperature characteristics of the variation of resonance frequency 共f r兲 for different oriented YCOB samples is shown in Fig. 4, over the temperature range of 30– 950 ° C. As can be observed, the resonance frequency shifted downward linearly with increasing temperature. The temperature coefficients of the resonance frequency were found to be on the order of −75 ⬃ − 95 ppm/ K, depending on the cuts. Figure 5 gives the effective extensional electromechanical coupling
TABLE I. Dielectric and piezoelectric properties for YCOB crystals with different orientations 共ZYwt兲 / 135°. Cut 共兲 r / 0 Loss d33 共pC/N兲 g33 共10−3 V m / N兲 keff Neff 共Hz m兲 Q
0° 10.7 0.001 1 11 2% 3000 18k
10°
20°
30°
40°
50°
60°
70°
80°
90°
11.4 0.001 2 20 1.5% 3000 13k
11.3 0.001 4.5 45 8.9% 2900 12k
10.9 0.001 6 62 11.7% 2800 12k
10.9 0.001 6.5 67 11.9% 2700 11k
10.5 0.001 5 54 9.6% 2600 13k
10.5 0.001 3.5 38 6.3% 2600 14k
11.5 0.001 2.5 25 1.3% 2700 13k
9.4 0.001 ⬍1 ⬃10 1.5% 2800 11k
9.0 0.001 ⬍1 ⬃10 2.0% 2800 10k
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FIG. 3. Resonance and antiresonance frequency characteristics of impedance and phase for a 共ZYwt兲40° / 135° oriented YCOB crystal at room temperature and 900 ° C 共inset兲.
factor as a function of temperature up to 950 ° C. The coupling factors were found to maintain their values up to 950 ° C, exhibiting a very stable piezoelectric properties in this temperature range. In summary, the oxyborate piezoelectric single crystal YCOB was grown using the Czochralski method. The melting temperature of YCOB was ⬃1500 ° C, prior to which, no phase transformation was observed. The dielectric permittivity and dielectric loss were found to be ⬃9 – 11 and ⬍0.1% at room temperature for YCOB crystals with different orientations, respectively. The coupling factor keff was found to be in the range of 1%–12%, with mechanical quality factors of 10– 18k for different orientations. YCOB exhibited high electrical resistivity at elevated temperatures, being ⬎2 ⫻ 108 ⍀ cm at 800 ° C. Together with its nearly temperature independent dielectric and piezoelectric properties and wide temperature usage range 共until its melting temperature, theoretically兲, this makes the oxyborate crystal family, such as YCOB, promising candidates for ultra high temperature sensing applications. The authors thank to W. Everson and J. Randi for the orientation and R. Xia for the sample preparation.
FIG. 4. Temperature characteristics of the resonance frequency for the YCOB crystal with different cuts.
FIG. 5. Temperature dependence of the effective electromechanical coupling factor for various YCOB crystal bars. 1
T. R. Shrout, R. Eitel, and C. A. Randall, Piezoelectric Materials in Devices, edited by N. Setter 共EPFL Swiss Federal Institute of Technology, Switzerland, 2002兲, p. 413. 2 R. C. Turner, P. A. Fuierer, R. E. Newnham, and T. R. Shrout, Appl. Acoust. 41, 299 共1994兲. 3 M. J. Schulz, M. J. Sundaresan, J. McMichael, D. Clayton, R. Sadler, and B. Nagel, J. Intell. Mater. Syst. Struct. 14, 693 共2003兲. 4 D. Damjanovic, Curr. Opin. Solid State Mater. Sci. 3, 469 共1998兲. 5 S. J. Zhang, J. Luo, D. W. Snyder, and T. R. Shrout, Handbook of Advanced Dielectric, Piezoelectric, and Ferroelectric Materials: Synthesis, Characterization and Applications, edited by Z. G. Ye, 共Woodhead, Cambridge, 2008兲, p. 130. 6 H. Kawanaka, H. Takeda, K. Shimamura, and T. Fukuda, J. Cryst. Growth 183, 274 共1998兲. 7 H. Ogi, N. Nakamura, K. Sato, M. Hirao, and S. Uda, IEEE Trans. Ultrason. Ferroelectr. Freq. Control 50, 553 共2003兲. 8 J. Bohm, E. Chilla, C. Flannery, H. Frohlich, T. Hauke, R. Heimann, M. Hengst, and U. Straube, J. Cryst. Growth 216, 293 共2000兲. 9 H. Fritze and H. L. Tuller, Appl. Phys. Lett. 78, 976 共2001兲. 10 E. Philippot, A. Ibanez, A. Goiffon, M. Cochez, A. Zarka, B. Capell, J. Schwartzel, and J. Detaint, J. Cryst. Growth 130, 195 共1993兲. 11 C. Reiter, P. Krempl, H. Thanner, W. Wallnofer, and P. Worsh, Ann. Chim. 共Paris兲 26, 91 共2001兲. 12 P. Krempl, G. Schleinzer, and W. Wallnofer, Sens. Actuators, A 61, 361 共1997兲. 13 Y. T. Fei, B. H. T. Chai, C. A. Ebbers, Z. M. Liao, K. I. Schaffers, and P. Thelin, J. Cryst. Growth 290, 301 共2006兲. 14 S. J. Zhang, J. G. Zhang, Z. X. Cheng, G. Y. Zhou, J. R. Han, and H. C. Chen, J. Cryst. Growth 203, 168 共1999兲. 15 G. Aka, F. Salin, and D. Pelenc, J. Opt. Soc. Am. B 14, 2238 共1997兲. 16 S. J. Zhang, Z. X. Cheng, and H. C. Chen, Defect Diffus. Forum, 186187, 79 共2000兲. 17 W. W. Ge, H. J. Zhang, J. Y. Wang, M. H. Jiang, S. Q. Sun, D. G. Ran, H. R. Xia, and R. I. Boughton, J. Appl. Crystallogr. 40, 125 共2007兲. 18 S. J. Zhang, Z. X. Cheng, J. R. Han, G. Y. Zhou, Z. S. Shao, C. Q. Wang, Y. T. Chow, and H. C. Chen, J. Cryst. Growth 206, 197 共1999兲. 19 J. Wang, X. Hu, X. Yin, R. Song, J. Wei, Z. Shao, Y. Liu, M. Jiang, Y. Tian, J. Jiang, and W. Huang, J. Mater. Res. 16, 790 共2001兲. 20 H. Takeda, H. Sako, H. Shimizu, K. Kodama, M. Nishida, H. Nakao, T. Nishida, S. Okamura, and T. Shikida, Jpn. J. Appl. Phys., Part 1 42, 6081 共2003兲. 21 H. Shimizu, T. Nishida, M. Nishida, H. Takeda, and T. Shiosaki, Jpn. J. Appl. Phys., Part 1 44, 7059 共2005兲. 22 C. Pawlaczyk, E. Markiewicz, A. Klos, W. Hofman, and A. Pajaczkowska, Phys. Status Solidi A 203, 2103 共2006兲. 23 Y. Qing and B. H. T. Chai, J. Cryst. Growth 197, 228 共1999兲. 24 IEEE Standard on Piezoelectricity, ANSI/EEE Standard 176, New York, 1987.
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