Dielectric and Electromechanical Properties of Rare Earth Calcium Oxyborate Piezoelectric Crystals at High Temperatures

State Key Lab. of Crystal Mater., Shandong Univ., Jinan, China
IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control (Impact Factor: 1.51). 05/2011; 58(4):868 - 873. DOI: 10.1109/TUFFC.2011.1881
Source: IEEE Xplore


The electrical resistivity, dielectric, and electromechanical properties of ReCa4O(BO3)3 (ReCOB; Re = Er, Y, Gd, Sm, Nd, Pr, and La) piezoelectric crystals were investigated as a function of temperature up to 1000°C. Of the studied crystals, ErCOB and YCOB were found to possess extremely high resistivity (p): p >; 3 × 107 ω.cm at 1000°C. The property variation in ReCOB crystals is discussed with respect to their disordered structure. The highest electromechanical coupling factor κ26 and piezoelectric coefficient d26 at 1000°C, were achieved in PrCOB crystals, with values being on the order of 24.7% and 13.1 pC/N, respectively. The high thermal stability of the electromechanical properties, with variation less than 25%, together with the low dielectric loss (<;46%) and high mechanical quality factor (>;1500) at elevated temperatures of 1000°C, make ErCOB, YCOB, and GdCOB crystals promising for ultrahigh temperature electromechanical applications.

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Available from: Shujun Zhang, Oct 14, 2014
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    • "on the other hand, the F v value of recoB crystals is much higher than that of lT (0.17 m 2 /c), being around 0.38 m 2 /c. It is of particular significance that recoB crystals were found to possess relatively high detectivity F d values, being on the order of 7.6 to 11.4 × 10 −5 pa −1/2 at room temperature , nearly two times those of TGs and lT, attributed to the low relative dielectric permittivity (9.5 to 15) and dielectric loss (<0.1%) [29], [30]. Furthermore, the detectivity F d values for ycoB, GdcoB, ndcoB, and prcoB crystals were determined to be on the order of 6.7 to 9.6 × 10 −5 pa −1/2 at 180°c, exhibiting high temperature stability , which will benefit pyroelectric sensor applications. "
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    ABSTRACT: Pyroelectric properties of the monoclinic ReCa4O(BO3)3 (ReCOB, where Re is rare earth: Y, Gd, Nd, and Pr) single crystals were investigated by the charge integration method in the temperature range of 20°C to 180°C. The two independent pyroelectric coefficients p1 and p3 were measured and their temperature-dependent properties were studied; the pyroelectric p1 was found to be negative and decrease with increasing temperature, varying from -59.3, -64.2, -65.5, and -59.5 μC/(m2??°C) at 30°C to -52.9, -53.3, -46.6, and -50.5 μC/(m2??°C) at 180°C for YCOB, GdCOB, NdCOB, and PrCOB, respectively, whereas the positive coefficient p3 was observed to decrease from 11.6, 13.6, 23.5, and 31.0 μC/(m2??°C) at 30°C to 2.5, 7.1, 4.9, and 10.1 μC/(m2??°C) at 180°C, respectively. In addition, the ReCOB crystals were found to possess relatively high detectivity Fd, being 7.6 to 11.4 x 10-5 Pa-1/2 at 30°C, approximately two times that of commercial triglycine sulfate (TGS) and LiTaO3 crystals, with minimal variations up to 180°C, indicating the potential for use in thermal imaging applications.
    Full-text · Article · Apr 2014 · IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control
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    ABSTRACT: Oxyborate single crystals, ReCa4O(BO3)3 (Re=La, Pr, Nd, Y. Gd), have recently been demonstrated to offer superior dielectric, piezoelectric and electromechanical properties to quartz, langasite and other commonly used piezoelectric crystals. Of particular significance is the ability to function at temperatures > 1000 o C, offering the potential for SAW, BAW and related sensors operational in harsh environments. In this work, the elasto-acoustic properties of oxyborate crystals were investigated as a function of rare earth cation. Crystallographic relationships were determined to be related to bond length and dependence of cation ordering, which was also reflected in the mechanical loss. Parameters related to high temperature operation, including electrical resistivity, dielectric loss, together with temperature dependent electromechanical and elastic properties were determined and discussed in relation to various applications.
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