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LGS Crystals Blanks or Blocks:
| X Direction | 5~40mm | Y Direction | 5~40mm |
| Z Direction | ~80mm | Direction Precision | ±20’ |
Langasite Slices:
| Diameter | 5~14mm | Frequency | 2.7~21MHz |
| Direction Precision | ±20’ | Surface Roughness(Lapped) | Ra=0.3~0.5μm |
Sensor, SAW Wafers:
| Diameter | 6~76.2mm | Thickness | 0.13~0.5mm |
| Reference Flat | 2~15mm | Surface Roughness (CMP single or double sides) | Ra≤1nm |
| Orientation | Following customer specifications |
Table 1. Basic Properties of Langasite
| Constant | Relative Dielectric Constant | Piezoelectric Constant (pC/N) | Elastic Stiffness (1011Pa) | |||||||
| 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 Parameters of Piezoelectric Crystals
| Crystals | Quartz SiO2 | Langasite La3Ga5SiO14 | Lithium tetraborate Li2B4O7 | Lithium Tantalite LiTa3 |
| 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, x103 | 100 | 50 | 10 | 2 |
| Temperature Frequency Coefficient TFC, x10-6/°C | 0.5 | 1.6 | 6.0 | 4.0 |
Table 3. SAW properties of Langasite and Quartz
| Crystals | Quartz(SiO2) | Langasite(La3Ga5SiO14) |
| Density (g/cm3) | 2.65 | 5.746 |
| SAW Velocity Vef (m/s) | (0º,132.75 º,0 º)3157 | (0º,140 º,25 º)2756 |
| K2emc,%(SAW) | 0.14 | 0.36 |
| Second order temp.coef. α2(x10-8/°C2) | -3.2 | -6.8 |
| Temp. Coef. TTO(°C) | 25 | 23 |
| Dielectric Constant (ε) | 4.92 | 27 |
| Power flow angle Ф, º | 0 | 0.5 |
Langasite crystal (La3Ga5SiO14, LGS), also called Lanthanum gallium silicate, belonging to the space group P321, point group 32, is a novel piezoelectric material with great potential for the fabrication of surface acoustic wave (SAW) and bulk acoustic wave (BAW) devices.
The LGS crystal has a higher electromechanical coupling factor (15.8%) than that of a quartz crystal, and the value indicates the effectiveness with which a piezoelectric material converts electrical energies into mechanical energies. It is also worth noting that the propagation velocities of a surface acoustic wave in LGS crystal is much lower, this value determines the filter size. When manufacturing quartz and LGS filters operating at the same center frequency, the geometrical dimensions of LGS filters can be made smaller, which conforms with the trend of the dense integration of modern electronics and saves production cost. In addition, The devices made of langasite crystal could be used at high temperatures up to 900℃ because of its high thermal stability.
Shanghai North Optics offers the LGS crystals blanks, polished substrates, and wafers upon customers' request.
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