Introduction

Lithium Niobate

Lithium niobate (LiNbO3) is a piezo-electric crystal, which is also ferro-electric. Its piezo-electric and electro-optic properties have wide applications. The low acoustic loss and high surface-wave velocity make LiNbO3 a good candidate for surface acoustic devices, such as SAW resonators, SAW filters a, SAW delay lines and SAW signal-compressors/expanders. As a piezo-electric transducer it is widely used in mirco-positioning, sensing and modulation applications.

As non-linear optical crystal, it can be used in frequency doublers, parametric oscillators, laser Q-switches and optical waveguide substrates.

Property Symbol Value Unit
Density ρ 4.64 g/cm3
Melting point Tm 1250 °C
Curie temperature Tc 1140 °C
Hardness   5 Moh

 

 

Lithium Tetraborate

Lithium tetraborate Li2B4O7 crystal (LBO) is a synthetic piezoelectric material having both fairly high electromechanical coupling coefficient (k) and zero temperature coefficient of delay (TCD).

The SAW reflectivity per aluminum strip on LBO substrate is at least 5 times greater than that of Lithium Niobate (LN), Lithium Tantalate (LT) and quartz, therefore the size of a chip for SAW devices can be reduced by 60%.

LBO crystal can be easily machined into standard wafer sizes by cutting, lapping and polishing, and is a suitable substrate for SAW and BAW devices in high frequency, low insertion loss, large effective bandwidth, high stability of central frequency and miniaturization for pager, cordless phone, cellular phone and data communication, etc.

Property Symbol Value Unit
Density ρ 2.44 g/cm3
Hardness   7 Moh
Transmission (0.3 ~ 2.2 μ)   55 ~ 90%  
Relative Dielectric Constant ε11 8.9  
Piezoelectric Constant s33 0.928 C/m2
Elastic Constant ce11 13.5 1010N/m2
Acoustic Velocity vac 3500 ~ 3860 m/s
Thermal Expansion Coefficient α11 11.1 10-6/℃
Preferred Orientations   <001><110><100>  

 

Comparative properties of piezoelectric crystals

Property \ 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

 

Lithium Niobate (LiNbO3), Li Tantalate (LiTaO3) and Li Tetraborate (LBO)

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