- Email: [email protected]
Dielectric, elastic and piezoelectric properties of SrLaGa3O7 and BaLaGa3O7 crystals with Melilite structure
Accepted Manuscript Dielectric, elastic and piezoelectric properties of SrLaGa3O7 and BaLaGa3O7 crystals with Melilite structure Chuanying Shen, Yuanyuan Zhang, Haohai Yu, Shujun Zhang, Wenwu Cao, Jiyang Wang, Huaijin Zhang PII:
S0925-8388(15)01518-2
DOI:
10.1016/j.jallcom.2015.05.219
Reference:
JALCOM 34403
To appear in:
Journal of Alloys and Compounds
Received Date: 28 February 2015 Revised Date:
14 May 2015
Accepted Date: 15 May 2015
Please cite this article as: C. Shen, Y. Zhang, H. Yu, S. Zhang, W. Cao, J. Wang, H. Zhang, Dielectric, elastic and piezoelectric properties of SrLaGa3O7 and BaLaGa3O7 crystals with Melilite structure, Journal of Alloys and Compounds (2015), doi: 10.1016/j.jallcom.2015.05.219. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT
Dielectric, elastic and piezoelectric properties of SrLaGa3O7 and BaLaGa3O7 crystals with Melilite structure Chuanying Shena, b, Yuanyuan Zhangc, Haohai Yua, Shujun Zhangb*, Wenwu Caob, Jiyang Wanga, and Huaijin Zhanga* State Key Laboratory of Crystal Materials, Institute of Crystal Materials, Shandong
University, Jinan, Shandong 250100, China. b
Materials Research Institute, Pennsylvania State University, University Park,
SC
Pennsylvania 16802, USA. c
RI PT
a
New Materials Research Institute, Shandong Academy of Sciences, Jinan, Shandong
*Corresponding authors:
M AN U
250014, China.
Huaijin Zhang and Shujun Zhang
E-mail: [email protected] (H. J. Zhang) and [email protected] (S. J. Zhang)
AC C
EP
TE D
Tel.: +86-531-88364684
ACCEPTED MANUSCRIPT Abstract: A full matrix of electromechanical properties of Melilite SrLaGa3O7 and BaLaGa3O7 crystals was evaluated by the impedance method, with minimal variations being observed for the two crystals. The
ε11T / ε 0 , d14 and k14 were determined to be 13.6, 9.4-9.5 pC/N and 17.1-17.4%, respectively. The
RI PT
relationship between electromechanical properties and microstructures was established to explain the elastic relationship, and piezoelectric origin. The optimized electromechanical properties were investigated in double rotated coordinate. The high resistivity (~108 Ohm·cm), high thermal stability of elastic constants (with variations of < 10%) and piezoelectric properties (with minimal variation of 8%)
SC
over the temperature range of 25-500 oC, making SrLaGa3O7 an attractive candidate for sensing
TE D
M AN U
applications at elevated temperatures.
AC C
EP
Keywords: Melilite crystal; Electromechanical properties; Elevated temperature; Sensing applications
ACCEPTED MANUSCRIPT 1. Introduction Piezoelectric materials find myriad applications in various electromechanical devices, such as energy harvesting, filters, transducers, resonators, actuators and sensors [1-7]. Piezoelectric single crystals, with high mechanical quality factor and high Curie temperature point, are attractive for
RI PT
high-temperature piezoelectric sensors. Among them, α-SiO2, GaPO4, Bi12SiO20, LiNbO3, Li2B4O7 (LBO), La3Ga5SiO14 (LGS), ReCa4O(BO3)3 crystals (Re = rare earth elements) etc. have been extensively investigated for sensing applications [8-15]. However, their piezoelectric applications at elevated temperatures (>500 oC) are limited by low piezoelectric coefficient, phase transitions, low
SC
electrical resistivity, low crystal symmetry, or strong interference of pyroelectric effect [16].
Recently, Melilite crystals with tetragonal system have attracted much attention for piezoelectric
M AN U
applications [17-20], where SrGdGa3O7 crystals were reported to exhibit high piezoelectric coefficient (d14 =14.5 pC/N), high electrical resistivity (>106 Ohm·cm at 600 oC) and high thermal stability (with variation of piezoelectric d14 < 20%) [18, 20], displaying advantages for high temperature sensing applications. However, investigations on piezoelectric properties of its homologous compounds SrLaGa3O7 and BaLaGa3O7 crystals at elevated temperature are limited, which is the target of this
TE D
work.
In this work, a full matrix of electromechanical properties of SrLaGa3O7 and BaLaGa3O7 crystals was determined by the impedance method. Furthermore, the optimized electromechanical properties
EP
were investigated in double rotated coordinates. In addition, the electrical resistivity and electromechanical properties were studied over a wide temperature range, and useful relationships between microstructure and physical properties were established.
AC C
2. Experiment details 2.1 Crystal growth
High-purity starting materials SrCO3, BaCO3, La2O3, Nd2O3 and Ga2O3 with stoichiometric proportions (an excess of 1vol% Ga2O3 was added to compensate the volatilization) were weighed, mixed, calcined (at 1050 oC for 10 hour to completely decompose the carbonates, such as SrCO3 and BaCO3), grinded and double mixed, subsequently pressed into tablets to synthesize SrNd0.01La0.99Ga3O7 (abbreviated as SrLaGa3O7) and BaNd0.01La0.99Ga3O7 (abbreviated as BaLaGa3O7) polycrystalline materials through conventional solid-state reaction [20]. The SrLaGa3O7 and BaLaGa3O7 single crystals were then grown by the Czochralski method through the stages of melting, seeding, necking,
ACCEPTED MANUSCRIPT shouldering, equal-diameter controlling, ending process, using an iridium crucible in an intermediate-frequency heated furnace (manufactured by Sichuan Foster Company). To prevent oxidation of the iridium crucible, the crystals were grown in an atmosphere of N2 containing low volume of O2 (to suppress the volatilization of Ga2O3 during the crystal growth process), about 2%. A 2
RI PT
kHz low radio-frequency furnace was used to heat the iridium crucible, and a Eurotherm model 818 controller/programmer was used to control the temperature of crucible, with a precision of 0.5 °C. The pulling speed and rotation rate were set to be 1-3 mm/h and 10-30 rpm, respectively. The grown crystals were cooled slowly down to room temperature at a rate of 10-20 °C/h after the growth process,
2.2 Characterization of piezoelectric properties 2.2.1 Room temperature electromechanical properties
SC
to avoid thermal cracking [20].
M AN U
Melilite crystals are in tetragonal phase with the space group 421 m , where the physical X-, Y- and Z-axes are parallel to the crystallographic a-, b- and c-axes. There are ten nonzero independent electromechanical constants, including two dielectric permittivities (ߝii), six elastic compliance constants (sij) and two piezoelectric coefficients (dij). The samples have the following dimensions: t (thickness) × w (width) × l (length) = 2.00 × 4.00 × 12.00 mm3 for long strips XYt5o, XYt45o, XY85o and ZXt45o, and t × w × l = 2.00 × 8.00 × 8.00 mm3 for X- and Z-cut square plates, according to the IEEE
TE D
standard on piezoelectricity [21]. The dielectric properties were calculated from capacitance measurements using an Agilent HP 4184A LCR meter at the frequencies of 100 Hz-100 kHz. The elastic, piezoelectric (calculated from length extension vibration) and electromechanical coupling factors were determined by impedance method, which were calculated from the resonance and anti-resonance frequencies of the specimens, using an Agilent HP 4194A impedance/gain-phase
EP
analyzer. The detailed measurements and computational formulas of impedance method were given in ref. [20]. In addition, the piezoelectric coefficients and coupling factors were also calculated based on face shear vibration mode by measuring the resonance frequency fr and anti-resonance frequency fa of
AC C
X- and Z-cut square plates, respectively. The electromechanical coupling factors k14 is given by [22-24]: 1
k14 = 1/ (1 + rp ) 2
where
1 f a2 − f r2 = r f r2
;
p=
(1) 4α 2 sE + sE [1 − 0.0691 × ( 22 E 33 )] 2 ( k0 + 2) 2 s44
is
a
correction
constant
with
1
α = 1 − 0.05015 × [( s22E + s33E ) / 2 s44E )] 2 , k0 = 2.0288. Piezoelectric d14 can be determined by the following equation: 1
E T 2 d14 = k14 ( s44 ε11 )
(2)
Similarly, k36 and d36 can be calculated using face shear vibrator of Z-cut samples. In this work the elastic compliance constants were determined by the impedance method, and the elastic stiffness constants (a reciprocal relationship to elastic compliance constants) can be calculated using the following formulas:
ACCEPTED MANUSCRIPT (3)
2 2 2 2 2 c12E = (- s13 + s12 ⋅ s33 )/(- s33 ⋅ s11 + 2s11 ⋅ s13 + s33 ⋅ s12 - 2s12 ⋅ s13 )
(4)
2 c13E = -s13 /(- 2s13 + s11 *s 33 + s12 *s33 )
(5)
2 c3E3 = (s11 + s12 )/(- 2s13 + s11 ⋅ s 33 + s12 ⋅ s 33 )
(6)
c44E = 1 s44
(7)
RI PT
2 2 2 2 2 c11E = ( s13 - s11 ⋅ s 33 )/(- s33 ⋅ s11 + 2s11 ⋅ s13 + s33 ⋅ s12 - 2s12 ⋅ s13 )
c44E = 1 s66
(8)
In addition to impedance method, the elastic stiffness constants of SrLaGa3O7 crystals were also determined by ultrasonic method, i.e., use longitudinal and shear wave transducers to measure the
SC
phase velocities along given crystal directions. Based on the theory of wave propagation in solids, the characteristic determinant of Christoffel equations are listed below: lm(c12 + c66 )
nl (c13 + c44 )
m c11 + n c44 + l c66 − ρ v 2
2
2
2
mn(c13 + c44 )
=0 mn(c13 + c44 ) (l 2 + m2 )c44 + n 2c33 − ρ v 2
M AN U
l 2c11 + n 2 c44 + m 2c66 − ρ v 2 lm(c12 + c66 ) nl (c13 + c44 )
(9)
where l, m and n are the direction cosines for the direction of propagation; ρ is the density of the crystal and v is the sound phase velocity.
E
When the wave propagates in the XY-plane, c12 can be calculated by the velocity of quasi-longitudinal wave of XY-cut samples rotated θ degree along the Z-direction by:
[(c 2 c11 + s 2 c66 − ρ v 2 ) ⋅ ( s 2c11 + c 2c66 − ρ v 2 )]0.5 − c66 sc Where c = cosine and s = sine of respective rotation angle.
TE D
c12E =
(10)
E
When the wave propagates in XZ-plane, c13 can be evaluated by ZX-cut samples rotated δ degree along the Y-direction using the following formula: [( s 2 c11 + c 2 c44 − ρ v 2 ) ⋅ ( s 2 c44 + c 2 c33 )]0.5 − c44 sc
EP
c13E =
(11)
In this paper, only diagonal components of the elastic stiffness constants were determined by the
AC C
ultrasonic method, using the X- and Z-cut samples. Table 1 lists the directions of wave propagation and polarization, and equations for the calculation of diagonal elastic stiffness constants. 2.2.2 Orientation dependence of electromechanical coefficients To optimize the electromechanical properties, the piezoelectric, dielectric and elastic coefficients were investigated in double rotated coordinates based on the determined electromechanical constants, using Matlab and Mathematica software.
2.2.3 Temperature dependent electromechanical properties The electrical resistivities were measured by the two-probe method using a source meter (Keithley 2410C, MetricTest, Hayward, CA) under an applied voltage of ±100 V. The temperature dependent electromechanical properties were investigated using an Impedance/gain-phase analyzer 4194A, which was connected to a specially designed Pt sample holder in a high temperature furnace (Vulcan 3-400HTA).
3. Results and discussion
ACCEPTED MANUSCRIPT 3.1 Room temperature electromechanical properties The compositions of as-grown crystals were measured using x-ray fluorescence analysis, with the formula being determined to be SrNd0.01La0.99Ga3O7 and BaNd0.01La0.99Ga3O7. Table 2 summarizes the electromechanical properties of SrLaGa3O7 and BaLaGa3O7 crystals measured by impedance and
RI PT
ultrasonic methods, and compared to commercially available α-SiO2. From Table2, the differences of electromechanical properties between SrLaGa3O7 and BaLaGa3O7 crystals are very small. The dielectric permittivity ε11T / ε 0 , piezoelectric constant d14 and electromechanical coupling factor k14 were determined to be 13.6, 9.3-9.4 pC/N and 17.1-17.4%, respectively. The piezoelectric constants are
SC
three to four times of magnitude higher than those of α-SiO2. It is important to point out that the piezoelectric and electromechanical coupling factors measured by length extension vibration of the
M AN U
long strips are comparable with the coefficients obtained by face shear vibration of square plates. The elastic stiffness constants calculated by impedance method are in good agreement with those of measured by the ultrasonic method. It is noted that the piezoelectric coefficients measured in this worked were found to be smaller than the reported values [20], most probably coming from the different segregation coefficients and crystal quality.
TE D
Electromechanical properties are closely related to the crystal structure, where SrLaGa3O7 was built up by GaO4 (regular and irregular) tetrahedral layers in XY-plane, being linked together along Z-axis by large Sr2+ and La3+ (distributed randomly with a ratio of 1:1) cations located in 8-fold coordinate sites, as shown in Fig. 1. The structure of BaLaGa3O7 crystal is similar to that of SrLaGa3O7, where Sr2+ and
EP
La3+ ions located in 8-fold coordinate sites [20].
AC C
The elastic stiffness reveals the bond strength of polyhedral units [25-27], and c11 is mainly determined by relatively rigid Ga-O tetrahedral layers which spreading in the XY-plane while c33 is mainly determined by the relatively soft 8-fold antiprisms which linking to the GaO4 tetrahedral layers. Thus, c11 is larger than c33 for both SrLaGa3O7 and BaLaGa3O7 crystals. In addition, the relatively shorter bond lengths of Ga-O and Sr-O (La-O) (as shown in table 3) in SrLaGa3O7 than those of Ga-O and Ba-O (La-O) in BaLaGa3O7, leading to a stronger bonding and thus larger elastic stiffness c11 and c33 of SrLaGa3O7 crystals [25]. SrLaGa3O7 and BaLaGa3O7 crystals possess similar piezoelectric anisotropy behaviors because of their similar crystals structure. Piezoelectric properties are closely related to the polyhedral model of the crystal structure and the distortion/rotation of these polyhedral units is the origin of piezoelectric
ACCEPTED MANUSCRIPT effect. With electric field being applied along the X- or Z-direction, the shear strain S4 (the distortion of relatively soft Sr-O, Ba-O antiprisms in YZ-plane) is larger than S6 (the distortion/rotation of rigid GaO4 tetrahedrons in XY-plane), as a result, piezoelectric d14 is larger than d36. Here, the “soft” and “rigid” mean longer Sr-O/Ba-O bond length (more compressive, thus smaller c44) and shorter Ga-O bond
3.2 Orientation dependence of electromechanical coefficients
RI PT
length (less compressive, thus larger c66), respectively [25].
For 42m symmetry, only two face shear piezoelectric coefficients d14 and d36 exist. However, piezoelectric coefficient d12* appeared in double rotated coordinate. After a rotation of angle α along
be determined using the following formula:
(12)
M AN U
d12* = d14 cos α sin α cos 3 β − ( d14 + d 36 ) cos α sin α cos β sin 2 β
SC
X-axis then rotated β along Z-axis for XY-cut, piezoelectric coefficient d12* in the new coordinate can
* in the double rotated coordinate Meanwhile, dielectric ε 11* and elastic compliance constant s22
were also investigated, using the following equations:
ε 11* = sin 2 β [ε 33 + (ε 11 − ε 33 )cos 2α ]+ε 11cos 2 β
(13)
* s22 = cos2 β {( s11 cos 4 α + s33 sin 4 α + ( s44 + 2s13 )sin 2 α cos2 α ]cos2 β − ( s12 cos2 α + s13 sin 2 α )sin 2 β }
(14)
TE D
+ sin 2 β [ s11 sin 2 β − ( s12 cos2 α + s13 sin 2 α ) cos2 β ] + sin 2 β cos2 β ( s66 cos2 α + s44 sin 2 α ) *
Fig. 2 (a) shows the orientation dependence of piezoelectric coefficient, where the highest d12 can be achieved for XYtw46o/1o-cuts with the value of 4.7 pC/N for SrLaGa3O7 crystals. Fig. 2(b) and Fig.
EP
2(c) give the dielectric and elastic compliance constants as a function of orientation, where the dielectric and elastic constants for XYtw46o/1o-cuts were determined to be 13.6 and 9.1 pm2 /N,
AC C
respectively. Fig. 2(d), (e) and (f) illustrate the rotation process from XY-cut to XYtw46o/1o-cut sample. 3.3 Temperature dependent electrical resistivity The melting point of SrLaGa3O7 and BaLaGa3O7 were reported to be 1650 oC [28] and 1560 oC [29], respectively. The general thermal stability of SrLaGa3O7 was investigated using TG/DTA, and no phase transition was observed prior to its melting point [20]. The electrical resistivities as a function of temperature were investigated in the temperature range of 300~700 oC, as given in Fig. 3, the resistivity of SrLaGa3O7 along Z-direction was found to be ~108 Ohm·cm at 500 oC. The resistivity along Z-direction is more than one time of magnitude higher than the value along X-direction, due to the GaO4 layered crystal structure, where the layers are linked by interconnected antiprisms vertical to the
ACCEPTED MANUSCRIPT Z-direction, which act as barriers against charge transport [25, 30]. The activation energies Ea can be calculated from the slopes of the curves and were found to be in the range of 1.07-1.14 eV for SrLaGa3O7 and BaLaGa3O7 crystals, related to the conductivity of the oxygen vacancies [31]. 3.4 Temperature dependent dielectric and piezoelectric properties
RI PT
Temperature dependent dielectric behaviors at frequency of 100 kHz for SrLaGa3O7 and BaLaGa3O7 crystals are shown in Fig. 4, in which the dielectric permittivities were found to increase as a function of temperature. The variation of dielectric permittivity along Z-axis of SrLaGa3O7 is only 12% from room temperature to 500 oC, revealing high temperature stability. The dielectric permittivity is closely
SC
associated with the electronic (the shifts of electron cloud) and ionic (the motions of cations and anions) polarization for simple inorganic materials. For SrLaGa3O7 and BaLaGa3O7 crystals with positive
M AN U
temperature coefficients of permittivity (TCߝ), the ionic polarization dominates [30, 32]. As shown in the inset of Fig. 4, the dielectric loss along the X-axis is much higher than that along the Z-axis, being associated with high electronic and ionic conductivity.
Determination the temperature dependence of the elastic constants is important for finding the optimized cut for zero temperature coefficients of resonant frequency, which are desirable for surface
TE D
acoustic wave (SAW) devices with stringent frequency stabilization requirements. Fig. 5 gives the elastic compliance constants for SrLaGa3O7 and BaLaGa3O7 crystals as a function of temperature from room temperature up to 500 oC. One can see that s11, s33, s44 and s66 increased slightly with increasing
EP
temperature, while s12 and s13 show the opposite tendency as the temperature increased, with the maximum variation of less than 10%, exhibiting a high thermal stability. Fig. 6 illustrates the
AC C
fundamental resonant frequency variation as a function of the rotation angle and temperature. The variation of resonance frequency decreased with increasing temperature, exhibiting a linear behavior, where the lowest temperature coefficient frequency (TCF) of 0.4 ppm/oC was achieved in XYt5o for SrLaGa3O7 crystals.
Fig. 7 shows the piezoelectric properties as a function of temperature for SrLaGa3O7 and
BaLaGa3O7 crystals. Of particular significance is that the piezoelectric coefficients d14 and d36 of SrLaGa3O7 were found to be nearly temperature independent, with minimal variations of 6% up to 500 o
C. On the other hand, the piezoelectric coefficients of BaLaGa3O7 crystals were found to increase
slightly with increasing temperature, with d14 being in the range of 9.5 to 10.3 pC/N.
4. Conclusions A full matrix of electromechanical properties of Melilite SrLaGa3O7 and BaLaGa3O7 crystals was
ACCEPTED MANUSCRIPT evaluated by impedance method, with minimal electromechanical property variations being observed for SrLaGa3O7 and BaLaGa3O7. The ε11T / ε 0 , d14 and k14 being determined to be 13.6, 9.4-9.5 pC/N and 17.1-17.4%, respectively. The elastic constants calculated by ultrasonic method are in good agreement with the values determined by the impedance method. The relationship between electromechanical
RI PT
properties and microstructures was established to explain the elastic relationship, and piezoelectric origin. In the structure of SrLaGa3O7 and BaLaGa3O7, a shorter bond length corresponds to a stronger bonding, then a larger elastic stiffness. With electric field being applied along the X- or Z-direction, the shear strain S4 is larger than S6, so d14 is larger than d36. Furthermore, the optimized piezoelectric,
SC
dielectric and elastic properties were investigated in double rotated coordinate. A high resistivity of ~108 Ohm·cm and a high thermal stability of piezoelectric coefficients with minimal variations of 8%
M AN U
were achieved over the range of 25-500 oC for SrLaGa3O7, superior to that of BaLaGa3O7 crystal,
Acknowledgment
TE D
making SrLaGa3O7 an attractive candidate for sensing applications at elevated temperatures.
EP
The authors would like to thank Professor Thomas R. Shrout for his helpful discussion. The authors from Shandong University acknowledged the National Natural Science Foundation of China (Grant No.
AC C
51372139). The author Y. Zhang acknowledged the National Natural Science Foundation of China (Grant No.51302158).
ACCEPTED MANUSCRIPT References [1] X. M. Wang, H. Tian, W. G. Xie, Y. Shu, W. T. Mi, M. A. Mohammad, Q. Y. Xie, Y. Yang, J. B. Xu, T. L. Ren, NPG Asia Mater. 7 (2015) e154. [2] E. W. Sun, S. J. Sang, Z. Y. Yuan, X. D. Qi, R. Zhang, W. W. Cao, J. Alloys Compd. 640 (2015) 64-67. [3] Z. Tylczyn´ski, M. Wiesner, J. Alloys Compd. 588 (2014) 177-181.
RI PT
[4] V. I. Aleshin, I. P. Raevski, J. Alloys Compd. 587 (2014) 138-142. [5] B. Riscob, Mohd. Shkir, V. Ganesh, N. Vijayan, K. K. Maury, K. Kishan Rao, G. Bhagavannarayana, J. Alloys Compd. 588 (2014) 242-247.
[6] Pharatree Jaita, Anucha Watcharapasorn, David P. Cann, Sukanda Jiansirisomboon, J. Alloys Compd. 596 (2014) 98-106.
SC
[7] J. F. Ma, X. Y. Liu, W. H. Li, J. Alloys Compd. 581 (2013) 642-645. [8] X. L. Bian, H. Jin, X. Z. Wang, S. R. Dong, G. H. Chen, J. K. Luo, M. J. Deen, B. S. Qi, Sci. Rep.-Uk. 5 (2015) 9123.
329-338.
M AN U
[9] F. P. Yu, Q. M. Lu, S. J. Zhang, H. W. Wang, X. F. Cheng, X. Zhao, J. Mater. Chem. C 3 (2015)
[10] S. J. Zhang, Y. Fei, B. H. T. Chai, E. Frantz, D. W. Snyder, X. N. Jiang, T. R. Shrout, Appl. Phys. Lett. 92 (2008) 202905.
[11] F. P. Yu, D. R. Yuan, X. L. Duan, L. M. Kong, X. Z. Shi, S. Y. Guo, L. H. Wang, X. F. Cheng, X. Q. Wang, J. Alloys Compd. 459 (2008) L1-L4.
[12] R. Machado, A. Di Loreto, A. Frattini, M. Sepliarsky, O. de Sanctis, M. G. Stachiotti, J. Alloys Compd. 621 (2015) 256-262.
TE D
[13] W. W. Ge, H. Liu, X. Y. Zhao, W. Z. Zhong, X. M. Pan, T. H. He, D. Lin, H. Q. Xu, X. P. Jiang, H. S. Luo, J. Alloys Compd. 462 (2008) 256-261. [14] Y. Liu, G. S. Xu, J. F. Liu, D. F. Yang, X. X. Chen, J. Alloys Compd. 603 (2014) 95-99. [15] S. J. Zhang and F. P. Yu, J. Am. Chem. Soc. 94 (2011) 3153-3170.
EP
[16] R. C. Turner, P. A. Fuierer, R. E. Newnham, T. R. Shrout, Appl. Acoust. 41 (1994) 299-324. [17] M. Hiroaki, H. Noguchi, T. Hoshina, H. Takeda, S. Fujihara, N. Kodama, T. Tsurumi, Jpn. J. Appl. Phys. 52 (2013) 09KD03.
AC C
[18] C. Y. Shen, H. J. Zhang, Y. Y. Zhang, J. Y. Wang, S. J. Zhang, T. R. Shrout, Electronic Packaging Technology (ICEPT), 2014 15th International Conference on IEEE2014.
[19] H. Takeda, M. Hagiwara, H. Noguchi, T. Hoshina, T. Takahashi, Appl. Phys. Lett. 102 (2013) 242907.
[20] Y. Y. Zhang, X. Yin, H. H. Yu, H. J. Cong, H. J. Zhang, J. Y. Wang, R. I. Boughton, Cryst. Growth Des. 12 (2011) 622-628. [21] IEEE Standard on Piezoelectricity, ANSI/IEEE Std 176-1987 (American Standards National Institute, New York, 1987). [22] R. Bechmann, Proc. Phys. Soc. B64 (1951) 323-337. [23] R. Bechmann, I. E. Fair Proceedings of the IRE New York, USA 46 (1958) 764-778. [24] S. J. Zhang, W. H. Jiang, R. J. M. Jr., F. Li, J. Luo, W. W. Cao, J. Appl. Phys. 110 (2011) 064106.
ACCEPTED MANUSCRIPT [25] C. Y. Shen, S. J. Zhang, D. L. Wang, T. X. Xu, H. Y. Hao, W. W. Cao, J. Y. Wang, H. J. Zhang, CrystEngComm 17 (2015) 1791-1799. [26] R. E. Newnham, Properties of Materials: Anisotropy, Symmetry and Structure (Oxford University, London, UK, 2005). [27] Z. Li, S-K. Chan, S. Ghose, Phys. Chem. Minerals. 17 (1990) 462-466. [28] A. V. Terentiev, P. V. Prokoshin, K. V. Yumashev, V. P. Mikhailov, W. Ryba-Romanowski, S.
RI PT
Golab, W. Pisarski, Appl. Phys. Lett. 67 (1995) 2442-2444. [29] W. Piekarczyk, M. Berkowski, G. Jasiole, J. Cryst. Growth 71 (1985) 395-398.
[30] C. Y. Shen, H. J. Zhang, H. J. Cong, H. H. Yu, J. Y. Wang, S. J. Zhang, J. Appl. Phys. 116 (2014) 044106.
[31] F. P. Yu, X. Zhao, L. Pan, F. Li, D. R. Yuan, S. J. Zhang, J. Phys. D: Appl. Phys. 43 (2010)
SC
165402.
[32] D. K. Kwon, Ph. D. Dissertation, Materials Science and Engineering Dept. The Pennsylvania
AC C
EP
TE D
M AN U
State University, 2006.
ACCEPTED MANUSCRIPT Table 1 The directions of wave propagation and polarization, and equations for the calculation of diagonal elastic stiffness constants of SrLaGa3O7 crystals. Sample
Type mode
Wave propagation
Direction
of
Equation
polarization
constants
for
longitudinal
X
X
c11 = ρ v12
Z-cut
longitudinal
Z
Z
c33 = ρ v22
X-cut
shear
X
Z
c55 = ρ v32
X-cut
shear
X
Y
c66 = ρ v42
AC C
EP
TE D
M AN U
SC
RI PT
X-cut
elastic
ACCEPTED MANUSCRIPT
Table 2 The electromechanical properties of SrLaGa3O7 and BaLaGa3O7 crystals measured by impedance and ultrasonic methods
Crystals
ε 11T / ε 0
ε 33T / ε 0
SrLaGa3O7
13.6
9.2
BaLaGa3O7
13.6
9.8
α-SiO2
4.5
4.6
Tanδ11
Tanδ33
SrLaGa3O7
0.2
0.01
BaLaGa3O7
0.4
0.02
RI PT
Dielectric Permittivities ߝii/ߝ0
SC
Dielectric Loss (%)
Elastic Compliance Constants sij (pm2 /N) E s12
SrLaGa3O7
7.9
-3.0
BaLaGa3O7
8.1
-3.0
α-SiO2
12.8
-1.8
E s13
E s 33
E s 44
E s 66
-1.9
7.6
24.9
16.4
-2.0
7.9
24.9
17.4
-1.2
9.6
20.0
29.1
c13E
c33E
E c44
E c66
6.3
16.3
4.0
6.1
---
17.4
4.1
6.3
15.8
4.0
5.7
M AN U
E s11
10
2
Elastic Stiffness Constants cij (10 N/m )
c12E
SrLaGa3O7 a
17.3
8.2
b
17.8
---
SrLaGa3O7
BaLaGa3O7
a
16.7
TE D
c11E
7.7
6.2 2
Piezoelectric Coefficients dij (pC/N) and eij (C/m ) d14 9.4
SrLaGa3O7
d
9.0
BaLaGa3O7
c
BaLaGa3O7d
d36
1.5
9.5
2.0
9.3
2.1
-0.7
AC C
α-SiO2
d11
1.5
EP
SrLaGa3O7
c
-2.3
Electromechanical coupling factors kij (%)
k14
k36
SrLaGa3O7
c
17.1
4.1
SrLaGa3O7
d
16.4
4.2
BaLaGa3O7
c
17.4
5.3
BaLaGa3O7
d
16.9
5.4
a
Measured by impedance method.
b c
Measured by ultrasonic method.
Calculated from length extension vibration of long bar.
d
Calculated from face shear of square plates.
ACCEPTED MANUSCRIPT Table 3 The cationic radius and average bond lengths in BaLaGa3O7 and SrLaGa3O7 crystals.
Crystal
SrLaGa3O7
Category
BaLaGa3O7
Sr2+/La3+
Ba2+/La3+
1.260/1.160
1.420/1.160
Cationic radius (Å) Ga-O
Sr/La-O
Ga-O
Ba/La-O
1.854
2.657
1.841
2.709
AC C
EP
TE D
M AN U
SC
RI PT
Average bond length (Å)
ACCEPTED MANUSCRIPT Fig. captions Fig. 1 (a) Projection of the average tetrahedral layers structure of SrLaGa3O7; (b) GaO4 regular tetrahedron (c) GaO4 irregular tetrahedron (d) 8-fold antiprism. Fig. 2 Piezoelectric, dielectric and elastic coefficients as a function of orientations for SrLaGa3O7 crystals.
RI PT
Fig. 3 Electrical resistivity as a function of temperature for SrLaGa3O7 and BaLaGa3O7 crystals.
Fig. 4 Variations of dielectric permittivity and dielectric loss as a function of temperature for SrLaGa3O7 and BaLaGa3O7 crystals.
SC
Fig. 5. Elastic compliance constants as a function of temperature for SrLaGa3O7 and BaLaGa3O7 crystals.
SrLaGa3O7 and BaLaGa3O7 crystals.
M AN U
Fig. 6. The variations of resonance frequency as a function of rotation angle and temperature for
AC C
EP
TE D
Fig. 7. Piezoelectric coefficients as a function of temperature for SrLaGa3O7 and BaLaGa3O7 crystals.
M AN U
SC
RI PT
ACCEPTED MANUSCRIPT
AC C
EP
TE D
Fig. 1
AC C
EP
TE D
M AN U
SC
Fig. 2
RI PT
ACCEPTED MANUSCRIPT
AC C
EP
TE D
M AN U
Fig. 3
SC
RI PT
ACCEPTED MANUSCRIPT
AC C
EP
TE D
M AN U
SC
Fig. 4
RI PT
ACCEPTED MANUSCRIPT
TE D
M AN U
SC
RI PT
ACCEPTED MANUSCRIPT
AC C
EP
Fig. 5
AC C
EP
TE D
M AN U
SC
Fig. 6
RI PT
ACCEPTED MANUSCRIPT
AC C
EP
TE D
M AN U
SC
Fig. 7
RI PT
ACCEPTED MANUSCRIPT
ACCEPTED MANUSCRIPT The electromechanical properties of SrLaGa3O7 and BaLaGa3O7 were evaluated.
AC C
EP
TE D
M AN U
SC
RI PT
The relationship between piezoelectricity and microstructures was established. The optimized piezoelectricity was investigated in double rotated coordinates.
S0925-8388(15)01518-2
DOI:
10.1016/j.jallcom.2015.05.219
Reference:
JALCOM 34403
To appear in:
Journal of Alloys and Compounds
Received Date: 28 February 2015 Revised Date:
14 May 2015
Accepted Date: 15 May 2015
Please cite this article as: C. Shen, Y. Zhang, H. Yu, S. Zhang, W. Cao, J. Wang, H. Zhang, Dielectric, elastic and piezoelectric properties of SrLaGa3O7 and BaLaGa3O7 crystals with Melilite structure, Journal of Alloys and Compounds (2015), doi: 10.1016/j.jallcom.2015.05.219. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT
Dielectric, elastic and piezoelectric properties of SrLaGa3O7 and BaLaGa3O7 crystals with Melilite structure Chuanying Shena, b, Yuanyuan Zhangc, Haohai Yua, Shujun Zhangb*, Wenwu Caob, Jiyang Wanga, and Huaijin Zhanga* State Key Laboratory of Crystal Materials, Institute of Crystal Materials, Shandong
University, Jinan, Shandong 250100, China. b
Materials Research Institute, Pennsylvania State University, University Park,
SC
Pennsylvania 16802, USA. c
RI PT
a
New Materials Research Institute, Shandong Academy of Sciences, Jinan, Shandong
*Corresponding authors:
M AN U
250014, China.
Huaijin Zhang and Shujun Zhang
E-mail: [email protected] (H. J. Zhang) and [email protected] (S. J. Zhang)
AC C
EP
TE D
Tel.: +86-531-88364684
ACCEPTED MANUSCRIPT Abstract: A full matrix of electromechanical properties of Melilite SrLaGa3O7 and BaLaGa3O7 crystals was evaluated by the impedance method, with minimal variations being observed for the two crystals. The
ε11T / ε 0 , d14 and k14 were determined to be 13.6, 9.4-9.5 pC/N and 17.1-17.4%, respectively. The
RI PT
relationship between electromechanical properties and microstructures was established to explain the elastic relationship, and piezoelectric origin. The optimized electromechanical properties were investigated in double rotated coordinate. The high resistivity (~108 Ohm·cm), high thermal stability of elastic constants (with variations of < 10%) and piezoelectric properties (with minimal variation of 8%)
SC
over the temperature range of 25-500 oC, making SrLaGa3O7 an attractive candidate for sensing
TE D
M AN U
applications at elevated temperatures.
AC C
EP
Keywords: Melilite crystal; Electromechanical properties; Elevated temperature; Sensing applications
ACCEPTED MANUSCRIPT 1. Introduction Piezoelectric materials find myriad applications in various electromechanical devices, such as energy harvesting, filters, transducers, resonators, actuators and sensors [1-7]. Piezoelectric single crystals, with high mechanical quality factor and high Curie temperature point, are attractive for
RI PT
high-temperature piezoelectric sensors. Among them, α-SiO2, GaPO4, Bi12SiO20, LiNbO3, Li2B4O7 (LBO), La3Ga5SiO14 (LGS), ReCa4O(BO3)3 crystals (Re = rare earth elements) etc. have been extensively investigated for sensing applications [8-15]. However, their piezoelectric applications at elevated temperatures (>500 oC) are limited by low piezoelectric coefficient, phase transitions, low
SC
electrical resistivity, low crystal symmetry, or strong interference of pyroelectric effect [16].
Recently, Melilite crystals with tetragonal system have attracted much attention for piezoelectric
M AN U
applications [17-20], where SrGdGa3O7 crystals were reported to exhibit high piezoelectric coefficient (d14 =14.5 pC/N), high electrical resistivity (>106 Ohm·cm at 600 oC) and high thermal stability (with variation of piezoelectric d14 < 20%) [18, 20], displaying advantages for high temperature sensing applications. However, investigations on piezoelectric properties of its homologous compounds SrLaGa3O7 and BaLaGa3O7 crystals at elevated temperature are limited, which is the target of this
TE D
work.
In this work, a full matrix of electromechanical properties of SrLaGa3O7 and BaLaGa3O7 crystals was determined by the impedance method. Furthermore, the optimized electromechanical properties
EP
were investigated in double rotated coordinates. In addition, the electrical resistivity and electromechanical properties were studied over a wide temperature range, and useful relationships between microstructure and physical properties were established.
AC C
2. Experiment details 2.1 Crystal growth
High-purity starting materials SrCO3, BaCO3, La2O3, Nd2O3 and Ga2O3 with stoichiometric proportions (an excess of 1vol% Ga2O3 was added to compensate the volatilization) were weighed, mixed, calcined (at 1050 oC for 10 hour to completely decompose the carbonates, such as SrCO3 and BaCO3), grinded and double mixed, subsequently pressed into tablets to synthesize SrNd0.01La0.99Ga3O7 (abbreviated as SrLaGa3O7) and BaNd0.01La0.99Ga3O7 (abbreviated as BaLaGa3O7) polycrystalline materials through conventional solid-state reaction [20]. The SrLaGa3O7 and BaLaGa3O7 single crystals were then grown by the Czochralski method through the stages of melting, seeding, necking,
ACCEPTED MANUSCRIPT shouldering, equal-diameter controlling, ending process, using an iridium crucible in an intermediate-frequency heated furnace (manufactured by Sichuan Foster Company). To prevent oxidation of the iridium crucible, the crystals were grown in an atmosphere of N2 containing low volume of O2 (to suppress the volatilization of Ga2O3 during the crystal growth process), about 2%. A 2
RI PT
kHz low radio-frequency furnace was used to heat the iridium crucible, and a Eurotherm model 818 controller/programmer was used to control the temperature of crucible, with a precision of 0.5 °C. The pulling speed and rotation rate were set to be 1-3 mm/h and 10-30 rpm, respectively. The grown crystals were cooled slowly down to room temperature at a rate of 10-20 °C/h after the growth process,
2.2 Characterization of piezoelectric properties 2.2.1 Room temperature electromechanical properties
SC
to avoid thermal cracking [20].
M AN U
Melilite crystals are in tetragonal phase with the space group 421 m , where the physical X-, Y- and Z-axes are parallel to the crystallographic a-, b- and c-axes. There are ten nonzero independent electromechanical constants, including two dielectric permittivities (ߝii), six elastic compliance constants (sij) and two piezoelectric coefficients (dij). The samples have the following dimensions: t (thickness) × w (width) × l (length) = 2.00 × 4.00 × 12.00 mm3 for long strips XYt5o, XYt45o, XY85o and ZXt45o, and t × w × l = 2.00 × 8.00 × 8.00 mm3 for X- and Z-cut square plates, according to the IEEE
TE D
standard on piezoelectricity [21]. The dielectric properties were calculated from capacitance measurements using an Agilent HP 4184A LCR meter at the frequencies of 100 Hz-100 kHz. The elastic, piezoelectric (calculated from length extension vibration) and electromechanical coupling factors were determined by impedance method, which were calculated from the resonance and anti-resonance frequencies of the specimens, using an Agilent HP 4194A impedance/gain-phase
EP
analyzer. The detailed measurements and computational formulas of impedance method were given in ref. [20]. In addition, the piezoelectric coefficients and coupling factors were also calculated based on face shear vibration mode by measuring the resonance frequency fr and anti-resonance frequency fa of
AC C
X- and Z-cut square plates, respectively. The electromechanical coupling factors k14 is given by [22-24]: 1
k14 = 1/ (1 + rp ) 2
where
1 f a2 − f r2 = r f r2
;
p=
(1) 4α 2 sE + sE [1 − 0.0691 × ( 22 E 33 )] 2 ( k0 + 2) 2 s44
is
a
correction
constant
with
1
α = 1 − 0.05015 × [( s22E + s33E ) / 2 s44E )] 2 , k0 = 2.0288. Piezoelectric d14 can be determined by the following equation: 1
E T 2 d14 = k14 ( s44 ε11 )
(2)
Similarly, k36 and d36 can be calculated using face shear vibrator of Z-cut samples. In this work the elastic compliance constants were determined by the impedance method, and the elastic stiffness constants (a reciprocal relationship to elastic compliance constants) can be calculated using the following formulas:
ACCEPTED MANUSCRIPT (3)
2 2 2 2 2 c12E = (- s13 + s12 ⋅ s33 )/(- s33 ⋅ s11 + 2s11 ⋅ s13 + s33 ⋅ s12 - 2s12 ⋅ s13 )
(4)
2 c13E = -s13 /(- 2s13 + s11 *s 33 + s12 *s33 )
(5)
2 c3E3 = (s11 + s12 )/(- 2s13 + s11 ⋅ s 33 + s12 ⋅ s 33 )
(6)
c44E = 1 s44
(7)
RI PT
2 2 2 2 2 c11E = ( s13 - s11 ⋅ s 33 )/(- s33 ⋅ s11 + 2s11 ⋅ s13 + s33 ⋅ s12 - 2s12 ⋅ s13 )
c44E = 1 s66
(8)
In addition to impedance method, the elastic stiffness constants of SrLaGa3O7 crystals were also determined by ultrasonic method, i.e., use longitudinal and shear wave transducers to measure the
SC
phase velocities along given crystal directions. Based on the theory of wave propagation in solids, the characteristic determinant of Christoffel equations are listed below: lm(c12 + c66 )
nl (c13 + c44 )
m c11 + n c44 + l c66 − ρ v 2
2
2
2
mn(c13 + c44 )
=0 mn(c13 + c44 ) (l 2 + m2 )c44 + n 2c33 − ρ v 2
M AN U
l 2c11 + n 2 c44 + m 2c66 − ρ v 2 lm(c12 + c66 ) nl (c13 + c44 )
(9)
where l, m and n are the direction cosines for the direction of propagation; ρ is the density of the crystal and v is the sound phase velocity.
E
When the wave propagates in the XY-plane, c12 can be calculated by the velocity of quasi-longitudinal wave of XY-cut samples rotated θ degree along the Z-direction by:
[(c 2 c11 + s 2 c66 − ρ v 2 ) ⋅ ( s 2c11 + c 2c66 − ρ v 2 )]0.5 − c66 sc Where c = cosine and s = sine of respective rotation angle.
TE D
c12E =
(10)
E
When the wave propagates in XZ-plane, c13 can be evaluated by ZX-cut samples rotated δ degree along the Y-direction using the following formula: [( s 2 c11 + c 2 c44 − ρ v 2 ) ⋅ ( s 2 c44 + c 2 c33 )]0.5 − c44 sc
EP
c13E =
(11)
In this paper, only diagonal components of the elastic stiffness constants were determined by the
AC C
ultrasonic method, using the X- and Z-cut samples. Table 1 lists the directions of wave propagation and polarization, and equations for the calculation of diagonal elastic stiffness constants. 2.2.2 Orientation dependence of electromechanical coefficients To optimize the electromechanical properties, the piezoelectric, dielectric and elastic coefficients were investigated in double rotated coordinates based on the determined electromechanical constants, using Matlab and Mathematica software.
2.2.3 Temperature dependent electromechanical properties The electrical resistivities were measured by the two-probe method using a source meter (Keithley 2410C, MetricTest, Hayward, CA) under an applied voltage of ±100 V. The temperature dependent electromechanical properties were investigated using an Impedance/gain-phase analyzer 4194A, which was connected to a specially designed Pt sample holder in a high temperature furnace (Vulcan 3-400HTA).
3. Results and discussion
ACCEPTED MANUSCRIPT 3.1 Room temperature electromechanical properties The compositions of as-grown crystals were measured using x-ray fluorescence analysis, with the formula being determined to be SrNd0.01La0.99Ga3O7 and BaNd0.01La0.99Ga3O7. Table 2 summarizes the electromechanical properties of SrLaGa3O7 and BaLaGa3O7 crystals measured by impedance and
RI PT
ultrasonic methods, and compared to commercially available α-SiO2. From Table2, the differences of electromechanical properties between SrLaGa3O7 and BaLaGa3O7 crystals are very small. The dielectric permittivity ε11T / ε 0 , piezoelectric constant d14 and electromechanical coupling factor k14 were determined to be 13.6, 9.3-9.4 pC/N and 17.1-17.4%, respectively. The piezoelectric constants are
SC
three to four times of magnitude higher than those of α-SiO2. It is important to point out that the piezoelectric and electromechanical coupling factors measured by length extension vibration of the
M AN U
long strips are comparable with the coefficients obtained by face shear vibration of square plates. The elastic stiffness constants calculated by impedance method are in good agreement with those of measured by the ultrasonic method. It is noted that the piezoelectric coefficients measured in this worked were found to be smaller than the reported values [20], most probably coming from the different segregation coefficients and crystal quality.
TE D
Electromechanical properties are closely related to the crystal structure, where SrLaGa3O7 was built up by GaO4 (regular and irregular) tetrahedral layers in XY-plane, being linked together along Z-axis by large Sr2+ and La3+ (distributed randomly with a ratio of 1:1) cations located in 8-fold coordinate sites, as shown in Fig. 1. The structure of BaLaGa3O7 crystal is similar to that of SrLaGa3O7, where Sr2+ and
EP
La3+ ions located in 8-fold coordinate sites [20].
AC C
The elastic stiffness reveals the bond strength of polyhedral units [25-27], and c11 is mainly determined by relatively rigid Ga-O tetrahedral layers which spreading in the XY-plane while c33 is mainly determined by the relatively soft 8-fold antiprisms which linking to the GaO4 tetrahedral layers. Thus, c11 is larger than c33 for both SrLaGa3O7 and BaLaGa3O7 crystals. In addition, the relatively shorter bond lengths of Ga-O and Sr-O (La-O) (as shown in table 3) in SrLaGa3O7 than those of Ga-O and Ba-O (La-O) in BaLaGa3O7, leading to a stronger bonding and thus larger elastic stiffness c11 and c33 of SrLaGa3O7 crystals [25]. SrLaGa3O7 and BaLaGa3O7 crystals possess similar piezoelectric anisotropy behaviors because of their similar crystals structure. Piezoelectric properties are closely related to the polyhedral model of the crystal structure and the distortion/rotation of these polyhedral units is the origin of piezoelectric
ACCEPTED MANUSCRIPT effect. With electric field being applied along the X- or Z-direction, the shear strain S4 (the distortion of relatively soft Sr-O, Ba-O antiprisms in YZ-plane) is larger than S6 (the distortion/rotation of rigid GaO4 tetrahedrons in XY-plane), as a result, piezoelectric d14 is larger than d36. Here, the “soft” and “rigid” mean longer Sr-O/Ba-O bond length (more compressive, thus smaller c44) and shorter Ga-O bond
3.2 Orientation dependence of electromechanical coefficients
RI PT
length (less compressive, thus larger c66), respectively [25].
For 42m symmetry, only two face shear piezoelectric coefficients d14 and d36 exist. However, piezoelectric coefficient d12* appeared in double rotated coordinate. After a rotation of angle α along
be determined using the following formula:
(12)
M AN U
d12* = d14 cos α sin α cos 3 β − ( d14 + d 36 ) cos α sin α cos β sin 2 β
SC
X-axis then rotated β along Z-axis for XY-cut, piezoelectric coefficient d12* in the new coordinate can
* in the double rotated coordinate Meanwhile, dielectric ε 11* and elastic compliance constant s22
were also investigated, using the following equations:
ε 11* = sin 2 β [ε 33 + (ε 11 − ε 33 )cos 2α ]+ε 11cos 2 β
(13)
* s22 = cos2 β {( s11 cos 4 α + s33 sin 4 α + ( s44 + 2s13 )sin 2 α cos2 α ]cos2 β − ( s12 cos2 α + s13 sin 2 α )sin 2 β }
(14)
TE D
+ sin 2 β [ s11 sin 2 β − ( s12 cos2 α + s13 sin 2 α ) cos2 β ] + sin 2 β cos2 β ( s66 cos2 α + s44 sin 2 α ) *
Fig. 2 (a) shows the orientation dependence of piezoelectric coefficient, where the highest d12 can be achieved for XYtw46o/1o-cuts with the value of 4.7 pC/N for SrLaGa3O7 crystals. Fig. 2(b) and Fig.
EP
2(c) give the dielectric and elastic compliance constants as a function of orientation, where the dielectric and elastic constants for XYtw46o/1o-cuts were determined to be 13.6 and 9.1 pm2 /N,
AC C
respectively. Fig. 2(d), (e) and (f) illustrate the rotation process from XY-cut to XYtw46o/1o-cut sample. 3.3 Temperature dependent electrical resistivity The melting point of SrLaGa3O7 and BaLaGa3O7 were reported to be 1650 oC [28] and 1560 oC [29], respectively. The general thermal stability of SrLaGa3O7 was investigated using TG/DTA, and no phase transition was observed prior to its melting point [20]. The electrical resistivities as a function of temperature were investigated in the temperature range of 300~700 oC, as given in Fig. 3, the resistivity of SrLaGa3O7 along Z-direction was found to be ~108 Ohm·cm at 500 oC. The resistivity along Z-direction is more than one time of magnitude higher than the value along X-direction, due to the GaO4 layered crystal structure, where the layers are linked by interconnected antiprisms vertical to the
ACCEPTED MANUSCRIPT Z-direction, which act as barriers against charge transport [25, 30]. The activation energies Ea can be calculated from the slopes of the curves and were found to be in the range of 1.07-1.14 eV for SrLaGa3O7 and BaLaGa3O7 crystals, related to the conductivity of the oxygen vacancies [31]. 3.4 Temperature dependent dielectric and piezoelectric properties
RI PT
Temperature dependent dielectric behaviors at frequency of 100 kHz for SrLaGa3O7 and BaLaGa3O7 crystals are shown in Fig. 4, in which the dielectric permittivities were found to increase as a function of temperature. The variation of dielectric permittivity along Z-axis of SrLaGa3O7 is only 12% from room temperature to 500 oC, revealing high temperature stability. The dielectric permittivity is closely
SC
associated with the electronic (the shifts of electron cloud) and ionic (the motions of cations and anions) polarization for simple inorganic materials. For SrLaGa3O7 and BaLaGa3O7 crystals with positive
M AN U
temperature coefficients of permittivity (TCߝ), the ionic polarization dominates [30, 32]. As shown in the inset of Fig. 4, the dielectric loss along the X-axis is much higher than that along the Z-axis, being associated with high electronic and ionic conductivity.
Determination the temperature dependence of the elastic constants is important for finding the optimized cut for zero temperature coefficients of resonant frequency, which are desirable for surface
TE D
acoustic wave (SAW) devices with stringent frequency stabilization requirements. Fig. 5 gives the elastic compliance constants for SrLaGa3O7 and BaLaGa3O7 crystals as a function of temperature from room temperature up to 500 oC. One can see that s11, s33, s44 and s66 increased slightly with increasing
EP
temperature, while s12 and s13 show the opposite tendency as the temperature increased, with the maximum variation of less than 10%, exhibiting a high thermal stability. Fig. 6 illustrates the
AC C
fundamental resonant frequency variation as a function of the rotation angle and temperature. The variation of resonance frequency decreased with increasing temperature, exhibiting a linear behavior, where the lowest temperature coefficient frequency (TCF) of 0.4 ppm/oC was achieved in XYt5o for SrLaGa3O7 crystals.
Fig. 7 shows the piezoelectric properties as a function of temperature for SrLaGa3O7 and
BaLaGa3O7 crystals. Of particular significance is that the piezoelectric coefficients d14 and d36 of SrLaGa3O7 were found to be nearly temperature independent, with minimal variations of 6% up to 500 o
C. On the other hand, the piezoelectric coefficients of BaLaGa3O7 crystals were found to increase
slightly with increasing temperature, with d14 being in the range of 9.5 to 10.3 pC/N.
4. Conclusions A full matrix of electromechanical properties of Melilite SrLaGa3O7 and BaLaGa3O7 crystals was
ACCEPTED MANUSCRIPT evaluated by impedance method, with minimal electromechanical property variations being observed for SrLaGa3O7 and BaLaGa3O7. The ε11T / ε 0 , d14 and k14 being determined to be 13.6, 9.4-9.5 pC/N and 17.1-17.4%, respectively. The elastic constants calculated by ultrasonic method are in good agreement with the values determined by the impedance method. The relationship between electromechanical
RI PT
properties and microstructures was established to explain the elastic relationship, and piezoelectric origin. In the structure of SrLaGa3O7 and BaLaGa3O7, a shorter bond length corresponds to a stronger bonding, then a larger elastic stiffness. With electric field being applied along the X- or Z-direction, the shear strain S4 is larger than S6, so d14 is larger than d36. Furthermore, the optimized piezoelectric,
SC
dielectric and elastic properties were investigated in double rotated coordinate. A high resistivity of ~108 Ohm·cm and a high thermal stability of piezoelectric coefficients with minimal variations of 8%
M AN U
were achieved over the range of 25-500 oC for SrLaGa3O7, superior to that of BaLaGa3O7 crystal,
Acknowledgment
TE D
making SrLaGa3O7 an attractive candidate for sensing applications at elevated temperatures.
EP
The authors would like to thank Professor Thomas R. Shrout for his helpful discussion. The authors from Shandong University acknowledged the National Natural Science Foundation of China (Grant No.
AC C
51372139). The author Y. Zhang acknowledged the National Natural Science Foundation of China (Grant No.51302158).
ACCEPTED MANUSCRIPT References [1] X. M. Wang, H. Tian, W. G. Xie, Y. Shu, W. T. Mi, M. A. Mohammad, Q. Y. Xie, Y. Yang, J. B. Xu, T. L. Ren, NPG Asia Mater. 7 (2015) e154. [2] E. W. Sun, S. J. Sang, Z. Y. Yuan, X. D. Qi, R. Zhang, W. W. Cao, J. Alloys Compd. 640 (2015) 64-67. [3] Z. Tylczyn´ski, M. Wiesner, J. Alloys Compd. 588 (2014) 177-181.
RI PT
[4] V. I. Aleshin, I. P. Raevski, J. Alloys Compd. 587 (2014) 138-142. [5] B. Riscob, Mohd. Shkir, V. Ganesh, N. Vijayan, K. K. Maury, K. Kishan Rao, G. Bhagavannarayana, J. Alloys Compd. 588 (2014) 242-247.
[6] Pharatree Jaita, Anucha Watcharapasorn, David P. Cann, Sukanda Jiansirisomboon, J. Alloys Compd. 596 (2014) 98-106.
SC
[7] J. F. Ma, X. Y. Liu, W. H. Li, J. Alloys Compd. 581 (2013) 642-645. [8] X. L. Bian, H. Jin, X. Z. Wang, S. R. Dong, G. H. Chen, J. K. Luo, M. J. Deen, B. S. Qi, Sci. Rep.-Uk. 5 (2015) 9123.
329-338.
M AN U
[9] F. P. Yu, Q. M. Lu, S. J. Zhang, H. W. Wang, X. F. Cheng, X. Zhao, J. Mater. Chem. C 3 (2015)
[10] S. J. Zhang, Y. Fei, B. H. T. Chai, E. Frantz, D. W. Snyder, X. N. Jiang, T. R. Shrout, Appl. Phys. Lett. 92 (2008) 202905.
[11] F. P. Yu, D. R. Yuan, X. L. Duan, L. M. Kong, X. Z. Shi, S. Y. Guo, L. H. Wang, X. F. Cheng, X. Q. Wang, J. Alloys Compd. 459 (2008) L1-L4.
[12] R. Machado, A. Di Loreto, A. Frattini, M. Sepliarsky, O. de Sanctis, M. G. Stachiotti, J. Alloys Compd. 621 (2015) 256-262.
TE D
[13] W. W. Ge, H. Liu, X. Y. Zhao, W. Z. Zhong, X. M. Pan, T. H. He, D. Lin, H. Q. Xu, X. P. Jiang, H. S. Luo, J. Alloys Compd. 462 (2008) 256-261. [14] Y. Liu, G. S. Xu, J. F. Liu, D. F. Yang, X. X. Chen, J. Alloys Compd. 603 (2014) 95-99. [15] S. J. Zhang and F. P. Yu, J. Am. Chem. Soc. 94 (2011) 3153-3170.
EP
[16] R. C. Turner, P. A. Fuierer, R. E. Newnham, T. R. Shrout, Appl. Acoust. 41 (1994) 299-324. [17] M. Hiroaki, H. Noguchi, T. Hoshina, H. Takeda, S. Fujihara, N. Kodama, T. Tsurumi, Jpn. J. Appl. Phys. 52 (2013) 09KD03.
AC C
[18] C. Y. Shen, H. J. Zhang, Y. Y. Zhang, J. Y. Wang, S. J. Zhang, T. R. Shrout, Electronic Packaging Technology (ICEPT), 2014 15th International Conference on IEEE2014.
[19] H. Takeda, M. Hagiwara, H. Noguchi, T. Hoshina, T. Takahashi, Appl. Phys. Lett. 102 (2013) 242907.
[20] Y. Y. Zhang, X. Yin, H. H. Yu, H. J. Cong, H. J. Zhang, J. Y. Wang, R. I. Boughton, Cryst. Growth Des. 12 (2011) 622-628. [21] IEEE Standard on Piezoelectricity, ANSI/IEEE Std 176-1987 (American Standards National Institute, New York, 1987). [22] R. Bechmann, Proc. Phys. Soc. B64 (1951) 323-337. [23] R. Bechmann, I. E. Fair Proceedings of the IRE New York, USA 46 (1958) 764-778. [24] S. J. Zhang, W. H. Jiang, R. J. M. Jr., F. Li, J. Luo, W. W. Cao, J. Appl. Phys. 110 (2011) 064106.
ACCEPTED MANUSCRIPT [25] C. Y. Shen, S. J. Zhang, D. L. Wang, T. X. Xu, H. Y. Hao, W. W. Cao, J. Y. Wang, H. J. Zhang, CrystEngComm 17 (2015) 1791-1799. [26] R. E. Newnham, Properties of Materials: Anisotropy, Symmetry and Structure (Oxford University, London, UK, 2005). [27] Z. Li, S-K. Chan, S. Ghose, Phys. Chem. Minerals. 17 (1990) 462-466. [28] A. V. Terentiev, P. V. Prokoshin, K. V. Yumashev, V. P. Mikhailov, W. Ryba-Romanowski, S.
RI PT
Golab, W. Pisarski, Appl. Phys. Lett. 67 (1995) 2442-2444. [29] W. Piekarczyk, M. Berkowski, G. Jasiole, J. Cryst. Growth 71 (1985) 395-398.
[30] C. Y. Shen, H. J. Zhang, H. J. Cong, H. H. Yu, J. Y. Wang, S. J. Zhang, J. Appl. Phys. 116 (2014) 044106.
[31] F. P. Yu, X. Zhao, L. Pan, F. Li, D. R. Yuan, S. J. Zhang, J. Phys. D: Appl. Phys. 43 (2010)
SC
165402.
[32] D. K. Kwon, Ph. D. Dissertation, Materials Science and Engineering Dept. The Pennsylvania
AC C
EP
TE D
M AN U
State University, 2006.
ACCEPTED MANUSCRIPT Table 1 The directions of wave propagation and polarization, and equations for the calculation of diagonal elastic stiffness constants of SrLaGa3O7 crystals. Sample
Type mode
Wave propagation
Direction
of
Equation
polarization
constants
for
longitudinal
X
X
c11 = ρ v12
Z-cut
longitudinal
Z
Z
c33 = ρ v22
X-cut
shear
X
Z
c55 = ρ v32
X-cut
shear
X
Y
c66 = ρ v42
AC C
EP
TE D
M AN U
SC
RI PT
X-cut
elastic
ACCEPTED MANUSCRIPT
Table 2 The electromechanical properties of SrLaGa3O7 and BaLaGa3O7 crystals measured by impedance and ultrasonic methods
Crystals
ε 11T / ε 0
ε 33T / ε 0
SrLaGa3O7
13.6
9.2
BaLaGa3O7
13.6
9.8
α-SiO2
4.5
4.6
Tanδ11
Tanδ33
SrLaGa3O7
0.2
0.01
BaLaGa3O7
0.4
0.02
RI PT
Dielectric Permittivities ߝii/ߝ0
SC
Dielectric Loss (%)
Elastic Compliance Constants sij (pm2 /N) E s12
SrLaGa3O7
7.9
-3.0
BaLaGa3O7
8.1
-3.0
α-SiO2
12.8
-1.8
E s13
E s 33
E s 44
E s 66
-1.9
7.6
24.9
16.4
-2.0
7.9
24.9
17.4
-1.2
9.6
20.0
29.1
c13E
c33E
E c44
E c66
6.3
16.3
4.0
6.1
---
17.4
4.1
6.3
15.8
4.0
5.7
M AN U
E s11
10
2
Elastic Stiffness Constants cij (10 N/m )
c12E
SrLaGa3O7 a
17.3
8.2
b
17.8
---
SrLaGa3O7
BaLaGa3O7
a
16.7
TE D
c11E
7.7
6.2 2
Piezoelectric Coefficients dij (pC/N) and eij (C/m ) d14 9.4
SrLaGa3O7
d
9.0
BaLaGa3O7
c
BaLaGa3O7d
d36
1.5
9.5
2.0
9.3
2.1
-0.7
AC C
α-SiO2
d11
1.5
EP
SrLaGa3O7
c
-2.3
Electromechanical coupling factors kij (%)
k14
k36
SrLaGa3O7
c
17.1
4.1
SrLaGa3O7
d
16.4
4.2
BaLaGa3O7
c
17.4
5.3
BaLaGa3O7
d
16.9
5.4
a
Measured by impedance method.
b c
Measured by ultrasonic method.
Calculated from length extension vibration of long bar.
d
Calculated from face shear of square plates.
ACCEPTED MANUSCRIPT Table 3 The cationic radius and average bond lengths in BaLaGa3O7 and SrLaGa3O7 crystals.
Crystal
SrLaGa3O7
Category
BaLaGa3O7
Sr2+/La3+
Ba2+/La3+
1.260/1.160
1.420/1.160
Cationic radius (Å) Ga-O
Sr/La-O
Ga-O
Ba/La-O
1.854
2.657
1.841
2.709
AC C
EP
TE D
M AN U
SC
RI PT
Average bond length (Å)
ACCEPTED MANUSCRIPT Fig. captions Fig. 1 (a) Projection of the average tetrahedral layers structure of SrLaGa3O7; (b) GaO4 regular tetrahedron (c) GaO4 irregular tetrahedron (d) 8-fold antiprism. Fig. 2 Piezoelectric, dielectric and elastic coefficients as a function of orientations for SrLaGa3O7 crystals.
RI PT
Fig. 3 Electrical resistivity as a function of temperature for SrLaGa3O7 and BaLaGa3O7 crystals.
Fig. 4 Variations of dielectric permittivity and dielectric loss as a function of temperature for SrLaGa3O7 and BaLaGa3O7 crystals.
SC
Fig. 5. Elastic compliance constants as a function of temperature for SrLaGa3O7 and BaLaGa3O7 crystals.
SrLaGa3O7 and BaLaGa3O7 crystals.
M AN U
Fig. 6. The variations of resonance frequency as a function of rotation angle and temperature for
AC C
EP
TE D
Fig. 7. Piezoelectric coefficients as a function of temperature for SrLaGa3O7 and BaLaGa3O7 crystals.
M AN U
SC
RI PT
ACCEPTED MANUSCRIPT
AC C
EP
TE D
Fig. 1
AC C
EP
TE D
M AN U
SC
Fig. 2
RI PT
ACCEPTED MANUSCRIPT
AC C
EP
TE D
M AN U
Fig. 3
SC
RI PT
ACCEPTED MANUSCRIPT
AC C
EP
TE D
M AN U
SC
Fig. 4
RI PT
ACCEPTED MANUSCRIPT
TE D
M AN U
SC
RI PT
ACCEPTED MANUSCRIPT
AC C
EP
Fig. 5
AC C
EP
TE D
M AN U
SC
Fig. 6
RI PT
ACCEPTED MANUSCRIPT
AC C
EP
TE D
M AN U
SC
Fig. 7
RI PT
ACCEPTED MANUSCRIPT
ACCEPTED MANUSCRIPT The electromechanical properties of SrLaGa3O7 and BaLaGa3O7 were evaluated.
AC C
EP
TE D
M AN U
SC
RI PT
The relationship between piezoelectricity and microstructures was established. The optimized piezoelectricity was investigated in double rotated coordinates.