Introduction

CTGS (Ca3TaGa3Si2O14) and CNGS  (Ca3TaGa3Si2O14)  are  piezoelectric crystals of the same crystal class as quartz. They are members of the so-called Langasite family with the general chemical formula A3BC3D2O14 as Langasite (LGS) and Langatate (LGT). Opposed to quartz they have no phase transition up to the melting point at about 1350°C. Therefore CTGS and CNGS are excellent candidates for high temperature piezoelectric sensors.

The isolation resistivity at higher temperatures is by 2 orders of magnitude better than that of LGT.

The CTGS and CNGS X-cuts have a piezoelectric factor d11 of about 4 ~ 5 pC/N, which is about twice the value of quartz. For rotated X-cuts the piezoelectric factor |d26| goes up to 11.5 pC/N. This feature allows the realization of high-temperature piezo sensors with very high sensitivity

For rotated Y-cuts the piezoelectric coupling factor k26 is much higher than that of quartz and reaches a maximum of 18.9% (CTGS) and 11.9% (CNGS). The theta-angle of zero TCF is about -30° for CTGS and -24.5° for CNGS.

CTGS and CNGS crystals are synthetically grown by the Czochralski method in boules up to 3" (76.2 mm)  mm diameter. Both crystals have excellent thermal, piezoelectric and dielectric properties and are resistant to many chemicals.

 

Dielectric, piezoelectric and elastic properties of CTGS and LGS 

Crystal

Relative

Dielectric Constant

Piezoelectric Constant

(pC/N)

Elastic Stiffness(1011 Pa)

ε11

ε33

d11

d14

c11

c12

c13

c14

c33

c44

CTGS

18.15

23.74

-4.58

10.43

1.232

0.330

0.448

0.004

1.781

0.409

LGS

18.96

50.19

5.66

-5.48

1.898

1.058

1.022

0.144

2.626

0.535

 

SAW properties of CTGS and LGS

 

Properties

LGS

CTGS

Density, g/cm3

5.746

4.66

SAW Velocity Veff, m/s

(Y-Cut)

2350

(Y-Cut)

2774

Electromechanical coupling factor 

K2emc, % (SAW)

0.3 ~ 0.38

0.322

Dielectric Constant e

19.62

16.7

 

 

For more detais please consult our Technical Notes on Novel Piezoelectric Materials

CTGS and CNGS Blanks & Wafers

Ca3TaGa3Si2O14 (CTGS) and Ca3NbGa3Si2O14 (CNGS) Wafers
Product

Diameter

[mm]

Thickness

[mm]

Cut

(Euler notation)

Surface

Quality

Flat

[mm]

Remarks
  76.2 0.500   SSP   SAW
  76.2 0.500   DSP   BAW
             

Caption:
SSP = Single Side Polished. Back side fine lapped
DSP = Double Side Polished
SAW = Surface Acoustic Wave Device
BAW = Bulk Acoustic Wave Device

 

Other dimensions, cut angles and other parameters on request. Please contact AXTAL