■ Features of langasite wafers
(1) 48.5°Y-26.7°X LGS (for SAW Device)
| • |
Equivalent temperature stability to ST-cut crystal |
| • |
Steep skirts of passband: the greatest feature of langasite wafers |
| • |
Lower insertion loss and wider passband compared with quartz: large electromechanical coupling coefficient K2 |
|
|
K2(%)
|
Phase Velocity(m/sec)
|
TCD(ppm/ºC)
|
PFA(º)
|
γ
|
|
48.5º Y-26.7º X LGS
|
0.31
|
2735
|
-1.1
|
-0.9
|
-0.85
|
|
ST Quartz
|
0.11
|
3158
|
0
|
0
|
0.38
|
|
X-112º YLT
|
0.72
|
3280
|
-20
|
1.2
|
-0.3
|
(2) Others
| • |
There is no phase transition to a high temperature region (1000°C or higher), and maintain piezoelectricity. |
Phase velocity and electromechanical coupling coefficient
Phase velocity and temperature coefficient
Distribution of phase velocity of SAW on 4-inch wafers
48.5° Y-26.7°X LGS
■ Characteristics of IF-SAW filter for base stations using langasite compared with a quartz filter
■ Applications of langasite wafers
Substrate for IF SAW filters
• IF filter for W-CDMA base stations
• IF filter for ground-wave digital TV base stations
• IF filter for satellite radio tuners
Substrate for high temperature sensors
• Temperature sensors
• Pressure sensors
• High temperature wireless sensors (SAW sensors)
• Other applications utilizing stable piezoelectricity at high temperatures
Characteristic comparison of various piezo-electric substrates
|
Crystal Dielectricity
|
Transition
|
temperature
|
K2(%)
|
d11(×10-12C/N)
|
Max usage temperature
|
Note
|
|
LiNbO3
|
ferroelectric
(pyroelectric)
|
1200ºC
|
4.5
|
|
~300ºC
|
decomposition
|
|
LiTaO3
|
ferroelectric
(pyroelectric)
|
610ºC
|
0.75
|
|
~300ºC
|
decomposition
|
|
α-Quartz
|
paraelectric
|
573ºC
|
0.16
|
-2.3
|
573ºC*
|
Phase transition
|
|
LBO
|
paraelectric
|
-
|
1.0
|
|
~230ºC
|
ion conduction
|
|
Langasite
|
paraelectric
|
-
|
0.44
|
-6.1
|
1470ºC
|
melting point
|
* 300ºC is actually the limit for quartz.
Congruent composition and decomposition
Combustion pressure sensor (Schematic)
Combustion pressure sensors (Provided by Cimeo Precision Co., Ltd. )
Concept of SAW sensor (for reference only)
Specifications of wafer
48.5Y-26.7X LGS
|
Cut direction
|
48.5°Y±0.5
|
|
Major orientation flat
|
26.7°X±0.5°
32mm±3mm
|
|
Sub orientation flat
|
11±3mm
|
|
Diameter
|
100.0mm±0.7mm
|
|
Thickness
|
500µm±30µm
|
|
Thickness version
|
<15µm
|
|
Sori
|
<60µm
|
|
Front surface
|
Mirror polished
|
|
Back surface
|
Lapping
|
|
