TY - GEN
T1 - Comparison of high temperature crystal lattice and bulk thermal expansion measurements of LGT single crystal
AU - Beaucage, T. R.
AU - Beenfeldt, E. P.
AU - Speakman, S. A.
AU - Porter, W. D.
AU - Payzant, E. A.
AU - Da Cunha, M. Pereira
PY - 2006
Y1 - 2006
N2 - Among the langasite family of crystals (LGX), the thee most popular materials are langasite (LGS, La3Ga5SiO14), langatate (LGT, La3Ga5.5Ta0.5O14) and langanite (LGN, La3Ga5.5Nb0.5O14). The LGX crystals have received significant attention for acoustic wave (AW) device applications due to several properties, which include: (1) piezoelectric constants about two and a half times those of quartz, thus allowing the design of larger bandwidth filters; (2) existence of temperature compensated orientations; (3) high density, with potential for reduced vibration and acceleration sensitivity; and (4) possibility of operation at high temperatures, since the LGX crystals do not present phase changes up to their melting point above 1400°C. The LGX crystals' capability to operate at elevated temperatures calls for an investigation on the growth quality and the consistency of these materials' properties at high temperature. One of the fundamental crystal properties is the thermal expansion coefficients in the entire temperature range where the material is operational. This work focuses on the measurement of the LGT thermal expansion coefficients from room temperature (25°C) to 1200°C. Two methods of extracting the thermal expansion coefficients have been used and compared: a.) dual push-rod dilatometry, which provides the bulk expansion; and b.) x-ray powder diffraction, which provides the lattice expansion. Both methods were performed over the entire temperature range and considered multiple samples taken from 〈001〉 Czochralski grown LGT material. The thermal coefficients of expansion were extracted by approximating each expansion data set to a third order polynomial fit over three temperature ranges reported in this work: 25°C to 400°C, 400°C to 900°C, 900°C to 1200°C. An accuracy of fit better than 35ppm for the bulk expansion and better than 10ppm for the lattice expansion have been obtained with the aforementioned polynomial fitting. The percentage difference between the bulk and the lattice fitted expansion responses over the entire temperature range of 25°C to 1200°C is less than 2% for the three crystalline axes, which indicates the high quality and growth consistency of the LGT crystal measured.
AB - Among the langasite family of crystals (LGX), the thee most popular materials are langasite (LGS, La3Ga5SiO14), langatate (LGT, La3Ga5.5Ta0.5O14) and langanite (LGN, La3Ga5.5Nb0.5O14). The LGX crystals have received significant attention for acoustic wave (AW) device applications due to several properties, which include: (1) piezoelectric constants about two and a half times those of quartz, thus allowing the design of larger bandwidth filters; (2) existence of temperature compensated orientations; (3) high density, with potential for reduced vibration and acceleration sensitivity; and (4) possibility of operation at high temperatures, since the LGX crystals do not present phase changes up to their melting point above 1400°C. The LGX crystals' capability to operate at elevated temperatures calls for an investigation on the growth quality and the consistency of these materials' properties at high temperature. One of the fundamental crystal properties is the thermal expansion coefficients in the entire temperature range where the material is operational. This work focuses on the measurement of the LGT thermal expansion coefficients from room temperature (25°C) to 1200°C. Two methods of extracting the thermal expansion coefficients have been used and compared: a.) dual push-rod dilatometry, which provides the bulk expansion; and b.) x-ray powder diffraction, which provides the lattice expansion. Both methods were performed over the entire temperature range and considered multiple samples taken from 〈001〉 Czochralski grown LGT material. The thermal coefficients of expansion were extracted by approximating each expansion data set to a third order polynomial fit over three temperature ranges reported in this work: 25°C to 400°C, 400°C to 900°C, 900°C to 1200°C. An accuracy of fit better than 35ppm for the bulk expansion and better than 10ppm for the lattice expansion have been obtained with the aforementioned polynomial fitting. The percentage difference between the bulk and the lattice fitted expansion responses over the entire temperature range of 25°C to 1200°C is less than 2% for the three crystalline axes, which indicates the high quality and growth consistency of the LGT crystal measured.
UR - http://www.scopus.com/inward/record.url?scp=39049135378&partnerID=8YFLogxK
U2 - 10.1109/FREQ.2006.275465
DO - 10.1109/FREQ.2006.275465
M3 - Conference contribution
AN - SCOPUS:39049135378
SN - 1424400740
SN - 9781424400744
T3 - Proceedings of the IEEE International Frequency Control Symposium and Exposition
SP - 658
EP - 663
BT - 2006 IEEE International Frequency Control Symposium and Exposition
PB - Institute of Electrical and Electronics Engineers Inc.
T2 - 2006 IEEE International Frequency Control Symposium and Exposition
Y2 - 4 June 2006 through 7 June 2006
ER -