Investigations of new materials, CTGS and CNGS, for SAW applications

Abstract

Recently, SAW material parameters have been reported for CNGS, CTGS, SNGS and STGS [1,2]. These materials are in the same family as LGS, LGN and LGT but have a lower density, differing coupling coefficients, higher velocity, and differing temperature coefficients. As compared with quartz, these materials have a higher density, lower velocity, higher electromechanical coupling coefficient, and higher temperature of operation without degradation of piezoelectric properties. Initial efforts have been made on investigating the various SAW parameters of CNGS and CTGS. Very little material is available, but very interesting properties have been found while investigating the Y-cut CNGS and CTGS substrates. It has been observed that there is a temperature compensated propagation angle near room temperature which is both promising in itself, as well as suggesting other compensated cuts may be possible at differing cut angles [2]. Electromechanical coupling, velocity, temperature coefficient of frequency, power flow angle, and fractional frequency curvature results are provided and compared with those of quartz. In addition, a comparison of previously published results for CNGS, CTGS, SNGS, and STGS Y-cut substrates are given. These results include coupling coefficient, velocity, capacitance, and reflectivity measurements for various propagation angles. These results are also compared with previously reported measurement for LGT and LGN and a discussion is provided.Based on reflectivity measurements and parameter extraction, a COM model is used to predict SAW resonator performance and fabricated SAW resonator results are provided and compared with the COM model. 0-7803-7922-5/03/$17.00 (c)

CTGS material parameters obtained by versatile SAW measurements

“…2 together with experimental data [3,6] for Y-cut CTGS with Euler angles (0°, -90°, ), where  is the propagation angle with respect to X-axis. Even though material constant set of [3] results in a simulated curve rather close to the experimental data points, the agreement is not yet sufficient to design modern SAW devices.…”

“…SAW phase velocity on shorted surface as a function of propagation angle  for Y-cut CTGS with Euler angles (0°, -90°, ). Red dots and black crosses: experimental data from [3,6]. Red, blue, and green lines: calculated velocities based on material constants from [3], [4], and [5], respectively.…”

Development of calculation model for designing temperature characteristics of double-layered thickness-shear resonator

“…[11][12][13][14][15] Since it does not undergo a phase transition up to a mp of around 1400 °C, it is expected to be applied to piezoelectric devices used in hightemperature environments. [16][17][18][19][20][21][22] However, the temperature stability of the resonant frequency of thickness-shear resonators using these materials was not necessarily sufficient.…”

Development of double layered thickness-shear resonator using langasite-type piezoelectric single crystal

“…So, it has been investigated as a piezoelectric material for application to pressure sensors and surface acoustic wave (SAW) devices operating at high temperature. [6][7][8][9][10][11][12] We have developed and evaluated Ca 3 Ta(Ga 1−x Al x ) 3 Si 2 O 14 [CTGAS] single crystals in which Al is substituted at the Ga site of Ca 3 TaGa 3 Si 2 O 14 [CTGS], one of the ordered langasitetype single crystals, in order to improve its characteristics as a piezoelectric device. [13][14][15][16][17][18] Then we found their attractive possibilities such as a resonator for timing device with smaller size, less power consumption, and shorter start-up time than quartz resonator.…”