Product Name: Piezoelectric Langasite La3Ga5SiO14 (LGSO) Crystal

Langasite La₃Ga₅SiO₁₄ crystals (LGSO or LGS), also known as Lanthanum gallium silicate, has its crystal structure belonging to the space group P321, point group 32. LGS is a promising piezoelectric material with no phase transitions up to its melting point of 1470 °C. LGSO has the value of electromechanical coupling coefficient, which is between that of a quartz crystal and that of lithium tantalate crystal. LGSO is mainly applied in fabrication of SAW (surface acoustic wave), BAW (bulk acoustic wave) devices and sensors (pressure sensor, acceleration sensor. etc.).

A list of the main applications of LGSO (LGS) include:

High Temperature SAW sensors
High Temperature BAW sensor
High Temperature and High-Sensitivity piezo-static sensor elements
Crystal units as BAW resonators with high motional capacitance
SAW devices for frequency control and selection
Wideband piezoelectric filters, both discrete and monolithic

Diameter: 10 - 60 mm, or can be customized

Thickness: 0.25-0.5 mm, or can be customized

Total Thickness Variation (TTV) for a 2" Wafer: < 10um

First Reference Flat: 15.0 mm

Second Reference Flat: 8.0 mm

Surface Roughness (Polished): Ra ≤ 1 nm

Surface Polish Choices: SSP or DSP.

Orientations: Euler angles (0°,138.5°,26.7°) or (0°,22°,90°), or Z-cut, or following customer specifications. Definition of Euler angles (0,138.5,26.6): 42.5 degree rotated Y-cut with reference flat perpendicular to 26.6 degree rotated X axis

Lead time: 6-8 weeks

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)
Constant	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^-6K^-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, %	0.25	0.90	4.00	7.00
Q-Factor Q, ~10³	100	50	10	2
Temperature Frequency Coefficient TFC, ~10^-6/C	0.5	1.6	6.0	4.0

Table 3 SAW properties of Langasite and Quartz

Properties (Crystal)	Quartz (SiO₂)	Langasite (La₃Ga₅SiO₁₄)
Density, g/cm³	2.65	5.746
SAW Velocity V_ef, m/s	(0°, 132.75°, 0°) 3157	(0°, 138.5°, 26.7°) 2723
Electromechanical coupling factor K²_emc, %(SAW)	0.14	0.36
Second order temp. coef. ñ₂, ~10^-8/up>2	-3.2	-6.8
Temp. Coef. T_TO,	25	23
Dielectric Constant	4.92	27
Power flow angle F, °	0	0.5

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Single Crystals and Substrates