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LGS Piezoelectric Crystal

Piezoelectric Crystal: Langasite (LGS)
Langastie crystal (La3Ga5SiO14, LGS), belonging to the space group P321, point group 32,  has been reported to be promising new piezoelectric materials for fabrication of surface acoustic wave (SAW) and bulk acoustic wave (BAW) devices. It is reported that devices made of langasite crystal could be used at a high temperature up to 900°C because of its high thermal stability.
? Basic Properties
Langasite crystal possesses some great properties, such as higher electromechanical coupling factor than quartz, no phase transition from room temperature to melt point. Some properties of langasite crystal are shown in Table 1.
Table 1 Dielectric, piezoelectric, elastic stiffness constants and their first order temperature coefficients of langasite crystal

Constant
Relative
Dielectric Constant
Piezoelectric Constant
(pC/N)
Elastic Stiffness(1011 Pa)
ε11
ε33
d11
d14
c11
c12
c13
c14
C33
C44
Value
18.96
50.19
5.66
-5.48
1.898
1.058
1.022
0.144
2.626
0.535
First Order Temp. Coef.
(10-6·K-1
150
-760
329
-342
-66
204
-75
-335
-94
-63

 

 



 

Table 2 Comparative properties of piezoelectric crystals

Properties \ Crystal
Quartz
SiO2
Langasite
La3Ga5SiO14
Lithium tetraborate
Li2B4O7
Lithium tantalate
LiTaO3
Electromechanical Coupling Factor K, %(BAW)
7.0
15.8
24.0
47.0
Frequency Spacing Δf, %
0.25
0.90
4.00
7.00
Q-Factor Q, ×103
100
50
10
2
Temperature Frequency Coefficient
 TFC, ×10-6/
0.5
1.6
6.0
4.0

With the rapid development of the communication technology, the new generation communication system enables people not only to talk, but also to transmit image, data and video. Langasite crystal possesses high SAW properties compared with quartz, which make it to be the most competitive material in this field. SAW properties of langasite and quartz are listed in the Table 3.
Table 3 SAW properties of langasite and Quartz
Properties \ Crystal
Quartz (SiO2)
Langasite (La3Ga5SiO14)
Density, g/cm3
2.65
5.746
SAW Velocity Vef, m/s
(0°, 132.75°, 0°)
3157
(0°, 140°, 25°)
2756
Electromechanical coupling factor K2emc, %(SAW)
0.14
0.36
Second order temp. coef.
α2, ×10-8/℃2
-3.2
-6.8
Temp. Coef. TTO, ℃
25
23
Dielectric Constant e
4.92
27
Power flow angle F, °
0
0.5

 

 

 

 

 

 

  ØProducts Information    

 

X  Direction

540 mm

Y  Direction

540 mm

 Deriction

80 mm

Direction Precision

±20¢

 

 

Diameter

514 mm

Frequency

2.721 MHz

Direction Precision

±20¢

Surface Roughness (Lapped)

Ra0.30.5 mm

Other sizes reflected in customer specifications

 

 

Diameter
6~101.6 mm
Thickness
0.13~0.5 mm
Reference Flat
2~15 mm
Surface Roughness
(Polished)
Ra≤1 nm
Orientation
following customer specifications
Other sizes reflected in customer specifications
 

 
 

 

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