Characterization of Neodymium Calcium Oxyborate Piezoelectric Crystal with Monoclinic Phase

Abstract

Piezoelectric crystals of neodymium calcium oxyborate, NdCa 4 O(BO 3 ) 3 (NdCOB), were grown by the Czochralski technique. The density was measured using the Archimedes method and found to be 3.63 g/cm 3 , in good agreement with the theoretical value. The thermal properties of NdCOB have been investigated, with the specific heat being on the order of 0.550 J/(g°C). The four thermal expansion coefficients were measured and found to be R 11 = 8.12, R 13 = 0.680, R 22 = 5.96, and R 33 =10.3 (10 -6 /°C), respectively. The relative dielectric permittivities were determined to be ε 11 T /ε 0 =9.90, ε 22 T /ε 0 =15.5, ε 33 T /ε 0 = 10.2, and ε 13 T /ε 0 = -1.60, respectively, with corresponding low dielectric loss at 100 kHz, being on the order of <0.1%. The complete set of dielectric, elastic, and piezoelectric constants for NdCOB single crystals were determined by the resonance method and compared to other oxyborate crystals ReCa 4 O(BO 3 ) 3 (Re = rare earth), where NdCOB exhibited relatively higher piezoelectric properties with d 13 = -4.8 pC/N, k 13 = 16.8%, d 26 = 16.5 pC/N, and k 26 = 31.1%, respectively. The relationship between piezoelectric property and structure was explored, in order to further improve the properties of ReCOB crystals.

High temperature ReCOB piezocrystals: Recent developments

“…Samples for dielectric and resistivity measurements are Y-cut, while the width shear vibration test is using (ZXw) y-cut bars, with dimensional The electrical resistance was measured using a Keithley (2410C) source meter, while dielectric properties were determined using a multifrequency LCR meter (HP4284A). The resonance and antiresonance frequencies of the shear mode resonators were measured using an Agilent HP 4294A impedance network analyzer, from which the electromechanical coupling k 26 , piezoelectric coefficient d 26 and mechanical quality factor Q could be calculated (in this article, only shear mode vibration is selected, because d 26 is the highest piezoelectric coefficient among all the coefficients [32] and the temperature dependent behavior is similar for all the parameters). The properties were measured as a function of temperature, with samples putting in a specially designed sample holder connected to high temperature furnace.…”

“…6 presents the electromechanical coupling factors (left) and piezoelectric coefficients (right) for (ZXw)-y cut NdCOB crystals as a function of temperature up to 950 1C. It was observed that both couplings and piezoelectric coefficients decreased with increasing temperature, with variation in the order of $20%, indicate NdCOB possesses deteriorate temperature dependent behavior, when compared to GdCOB and YCOB crystals, possibly due to its disordered structure, induced by the similar ion radius of Nd 3 + and Ca 2 + [32]. Fig.…”

“…Large size and high quality crystals can be readily grown by the Czochralski growth method [20][21][22][23]. Oxyborate crystals have been preliminary investigated for optical applications [20][21][22][23], with their piezoelectric properties evaluated at temperatures o200 1C [24][25][26][27][28][29][30][31][32][33]. Recently, oxyborate crystals were reported to possess very high resistivities, being in the order of $ 10 6 Ohm cm at elevated temperature of 1200 1C, demonstrating promising materials for high temperature applications [34][35][36][37].…”

Growth and piezoelectric properties of TmCOB single crystals

“…Recently, rare-earth calcium oxyborate crystals ReCa 4 O(BO 3 ) 3 (ReCOB, Re:rare-earth elements) have been reported to be promising for high temperature piezoelectric sensor applications, due to the merits of high electrical resistivity at elevated temperatures (>10 8 Ω·cm@900 o C), high piezoelectric coefficients (~16 pC/N), high electromechanical coupling factors (~31%), and high temperature stability of piezoelectric and electromechanical properties up to 1000 o C [1][2][3][4][5][6][7][8].…”

Pyroelectric properties of ReCOB and BiBO oxyborate crystals with monoclinic symmetry

“…Among oxyborate crystals, rare-earth calcium oxyborate crystals ReCa 4 O(BO 3 ) 3 (ReCOB, Re: Rare-earth) with monoclinic phase and space group C m were extensively investigated, due to their attractive properties for optical and piezoelectric applications [7][8][9][10][11][12][13][14]. Besides, ReCOB was reported to possess congruent melting point (~1500 o C), thus can be readily grown into large size crystals (3~4 inches diameter) by traditional Czochralski and Bridgeman methods [2,15,16].…”