科研之友
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摘要
A full set of langatate (LGT) elastic, dielectric, and piezoelectric constants with their respective temperature coefficients up to 900 degrees C is presented, and the relevance of the dielectric and piezoelectric constants and temperature coefficients are discussed with respect to predicted and measured high-temperature SAW propagation properties. The set of constants allows for high-temperature acoustic wave (AW) propagation studies and device design. The dielectric constants and polarization and conductive losses were extracted by impedance spectroscopy of parallel-plate capacitors. The measured dielectric constants at high temperatures were combined with previously measured LGT expansion coefficients and used to determine the elastic and piezoelectric constants using resonant ultrasound spectroscopy (RUS) measurements at temperatures up to 900 degrees C. The extracted LGT piezoelectric constants and temperature coefficients show that e(11) and e(14) change by up to 62% and 77%, respectively, for the entire 25 degrees C to 900 degrees C range when compared with room-temperature values. The LGT high-temperature constants and temperature coefficients were verified by comparing measured and predicted phase velocities (v(p)) and temperature coefficients of delay (TCD) of SAW delay lines fabricated along 6 orientations in the LGT plane (90 degrees, 23 degrees,Psi) up to 900 degrees C. For the 6 tested orientations, the predicted SAW v(p) agree within 0.2% of the measured v(p) on average and the calculated TCD is within 9.6 ppm/degrees C of the measured value on average over the temperature range of 25 degrees C to 900 degrees C. By including the temperature dependence of both dielectric and piezoelectric constants, the average discrepancies between predicted and measured SAW properties were reduced, on average: 77% for v(p), 13% for TCD, and 63% for the turn-over temperatures analyzed.
- 出版日期2013-4
