18. High-Quality 2 Inch La3Ga5.5Ta0.5O14 and Ca3TaGa3Si2O14 Crystals for Oscillators and Resonators
- Sheng Yao,
- Bruce Tuttle,
- Clive Randall and
- Dwight Viehland
Published Online: 26 MAR 2008
Copyright © 2005 The American Ceramic Society
Advances in Electronic Ceramic Materials: Ceramic Engineering and Science Proceedings, Volume 26, Number 5
How to Cite
Klemenz, C. F., Luo, J. and Shah, D. (2005) High-Quality 2 Inch La3Ga5.5Ta0.5O14 and Ca3TaGa3Si2O14 Crystals for Oscillators and Resonators, in Advances in Electronic Ceramic Materials: Ceramic Engineering and Science Proceedings, Volume 26, Number 5 (eds S. Yao, B. Tuttle, C. Randall and D. Viehland), John Wiley & Sons, Inc., Hoboken, NJ, USA. doi: 10.1002/9780470291252.ch18
- Published Online: 26 MAR 2008
- Published Print: 1 JAN 2005
Print ISBN: 9781574982350
Online ISBN: 9780470291252
Ca3Ga2Ge4O14(CGG)-type crystals have attracted much attention over the past years for their outstanding piezoelectric properties, superior to quartz, offering new possibilities in bulk (BAW) and surface acoustic wave (SAW) devices. Among them, most investigated are the isomorphs La3Ga5SiO14 (LGS), La3Ga5.5Nb0.5O14 (LGN), and La3Ga5.5Ta0.5O14 (LGT), so-called langasites, commonly denoted herein LGX (X = S, N, and T). Recently, the quaternary CGG isomorphs, Ca3TaGa3Si2O14 (CTGS) and Ca3NbGa3Si2O14 (CNGS) became of interest as they have an ordered crystal structure that may lead to a better consistency in acoustic properties and a higher Q than LGT. Today, the main limitation towards commercialization of any of these new piezoelectrics is the insufficient homogeneity of the crystals, which lead to non-reliable materials parameters measurements and a spread in device characteristics.
We report on the growth of high-quality large-diameter 2′ LGT and 1.5′ CTGS crystals. The study of inherent and growth-induced crystal defects combined with systematic Czochralski growth process optimization have led to these colorless transparent crystals. The high-quality of the LGT crystals was confirmed by X-ray synchrotron topography.
The LGT crystals were processed into Y-cut plano-convex resonators by MtronPTI (Orlando). The Q·f product was measured from fundamental to 9th overtone. Values exceeding the limit of AT- and SC-cut quartz were obtained.