Doubly Rotated Blanks
Doubly Rotated Blanks are single crystal cultured quartz blanks fabricated with a double angular rotation suitable for operation in the thickness shear mode. This family of blanks includes the SC-cut and IT-cut and is designed to reduce the effects of stress on resonant frequency.
Doubly rotated blanks can be fabricated to a range of specifications for either of the two angles of rotation as well as the overall blank dimensions. Typical specifications for the j -rotation (i.e. the first, or X to X', rotation) are around 22° for SC-cut blanks and 19° for IT-cuts, but can vary by as much as ±10. The q -rotation (i.e. the second, or Z to Z' rotation) typically ranges from 33° to 35°. Verification of specified orientation is assured by providing us with the appropriate x-ray diffraction reference standards. As the blanks are usually angle corrected after delivery, both surfaces are lapped to a rough finish using 15 µm abrasive, unless otherwise specified.
Typical Specifications
Mechanical Characteristics
| Units | Typical Values | Tolerance | |
|---|---|---|---|
| X-height x Z-width | mm | 16.5 x 16.5 | ± 0.25 |
| Thickness, t | As specified | ± 0.013 | |
| Orientation - φ | degrees | As specified (18°-24°) | ± 10 minutes |
| Orientation - θ | degrees | As specified (33±-35°) | ± 5 minutes |
| Standard dimensions (other dimensions are available to meet customer-specific requirements) | |||
Material Characteristics
| Handedness | Right | |||
|---|---|---|---|---|
| Infrared a (3500 cm-1) | α - units | Grade B: 0.045 | maximum | |
| Grade l | ||||
| Inclusions (diameter) | 25 - 75 µm | cm³ | 4 | |
| 75 - 100 µm | cm³ | 2 | ||
| >100 µm | cm³ | 2 | ||
| Etch Channels | cm² | Grade 4: 300 | maximum | |
| Twins in useful volume | Count | None | ||
Surface Characteristics
- Surface Finish: rough lapped using 15 µm abrasive.
- Chips intruding onto surface: 1.0 mm Maximum
Seed Characteristics
- Pure - Z, seed free material
References
International Electrotechnical Commission Standard, CEI/IEC 758, Second edition, 1994.
Institute of Electrical and Electronic Engineers Standard on Piezoelectricity, ANSI/IEEE Std. 176-1 987.