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: 1.5). 05/2011; 58(4):868 - 873. DOI: 10.1109/TUFFC.2011.1881
Source: IEEE Xplore

ABSTRACT 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.

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Piezoelectric single crystals Ca3TaGa3Si2O14 (CTGS) and YCa4O(BO3)3 (YCOB)were grown by the Czochralski pulling method and specially cut into three types of resonator samples with different vibration modes (CTGS lateral mode, YCOB thickness shear mode and planar mode). The dielectric, elastic and piezoelectric properties of the resonators have been investigated as functions of temperature (up to 800 °C) and vacuum pressure (down to 10−10 Bar). It was found that all the crystal resonators have excellent stability in the test range of vacuum pressure level; and their fundamental resonant frequencies exhibit temperature dependent characteristics, some of which were linear. It is also found that for CTGS lateral mode, YCOB thickness shear mode and YCOB planar mode resonators, the relative dielectric permittivity ε11T/ε0, ε22T/ε0, ɛ T/ɛ 0 are 17.0–18.2 (17.6 ± 0.6), 13.5–24.4 (19.0 ± 5.5), 14.0–16.9 (15.4 ± 1.5); the elastic coefficients S11E, S66E, SE are 8.8–9.3 (9.1 ± 0.3), 16.3–17.3 (16.8 ± 0.5), 8.3–9.2 (8.8 ± 0.5) (pm2/N); and the piezoelectric coefficients d11, d26, d are 3.7–3.9 (3.8 ± 0.1), 8.8–10.9 (9.9 ± 1.0), 3.3–3.9 (3.6 ± 0.3)(pC/N), respectively. Mechanical quality factor Q was found to be 4500–7000 and 6000–11,000 for CTGS and YCOB, respectively. The excellent property stability of these CTGS and YCOB piezoelectric resonators, especially the thickness shear mode, make them very promising candidates for sensing applications at high-temperature and high-vacuum conditions.
    Sensors and Actuators A Physical 09/2014; 216:167–175. DOI:10.1016/j.sna.2014.05.017 · 1.94 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: High-temperature sensors are desirable for structural health monitoring and/or nondestructive evaluation of next-generation turbines, more efficient jet engines, and the furnace components of electrical power plants. Of all the investigated high-temperature piezoelectric materials, rare-earth calcium oxyborate crystals ReCa4O(BO3)3 (ReCOB, Re: rare-earth) exhibit attractive advantages for high-temperature piezoelectric sensing. In this paper, the electroelastic properties of different ReCOB piezoelectric crystals are investigated. The crosstalk between various vibration modes are discussed, from which the optimized crystal cuts are achieved. Furthermore, temperature dependences of the electrical resistivity, dielectric, elastic, piezoelectric, and electromechanical properties of ReCOB crystals are studied. Finally, the thermal properties, including thermal expansion, specific heat, and thermal conductivity at elevated temperatures are studied and compared with commercially available high-temperature piezoelectric crystals.
    IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control 08/2014; 61(8):1344-1356. DOI:10.1109/TUFFC.2014.3042 · 1.50 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Thulium calcium oxyborate crystals TmCa4O(BO3)3 (TmCOB) were desigend and grown by using the Czochralski pulling method. Thermal properteis were characterized, where the thermal expansions were measured to be on the order of α11=7.96, α22=4.86 and α33 =10.32×10-6/C. Meanwhile, the thermal conductivity κ and thermal diffusivity λ were evaluated to be 2.17 W/(m•oC) and 0.76mm2/s along Y-axis at room temperature. In addition, the dielectric, elastic and piezoelectric performances were investigated by impedance method, where the piezoelectric charge coefficients were determined to be on the order of d11=1.7, d12=3.8, d13=-4.2, d15=-0.92, d24=4.9, d26=7.8, d31=-0.75, d32=-2.4, d33=2.2 and d35=-5.2 pC/N. Moreover, temperature dependent electrical resistivity and electro-elastic properties were studied from room temperature to 900oC, where high electrical resistivity of ~6×107Ω•cm and low dielectric loss ~21% were achieved at 900oC, with high thermal stability of electromechanical coupling factors and piezoelectric coefficients over the temperature range of 20oC-900oC. All these properties demonstrate TmCOB crystals an attractive candidate for high temperature sensor fabrications.
    CrystEngComm 10/2014; 17(3). DOI:10.1039/C4CE01830C · 3.86 Impact Factor


Available from
Oct 14, 2014