The crystal langasite manifests its unique advantages and potentials for high temperature applications due to a high electromechanical coupling coefficient, temperature compensated orientations for surface acoustic wa...The crystal langasite manifests its unique advantages and potentials for high temperature applications due to a high electromechanical coupling coefficient, temperature compensated orientations for surface acoustic wave （SAW）, and temperature stability. In order to analyze the pressure-induced frequency shift in SAW resonator type sensors at high temperature, this paper presents the electroelastic wave equations employing the effective material constants for small vibrations superimposed on biases originated from homogeneous temperature and external pressure fields in the Lagrangian description. Incorporated with the first-order perturbation integration, a model including both the mechanical and electrical perturbation items originating from thermal biases and small pressure fields is proposed. This universal model is suitable for substrate with high piezoelectricity and can be applied at either room temperature or high temperature circumstance. The criteria of optimal cuts for SAW pressure sensitivity, i.e., high electromechanical coupling coefficient and low temperature coefficient of delay, are proposed. A thorough investigation in trebly rotated cuts has shown that optimal pressure sensitive crystallographic areas can be obtained. The areas suitable for pressure sensors at room temperature are defined with Euler angles Ω1： φ=0°-0.6°, θ=144.4°-145.8°, ψ =23.2°-24.1°,Ω2： φ=59.4°-61.°, θ=34.2°-36.2°, ψ =24.1°-22.3°,Ω3： φ=119°-120°, θ=143.8°-145.5°, ψ =22.3°-23.5° The areas suitable for pressure sensors at high temperature are defined with Euler angles Ⅰ： φ=8°-30°, θ=24°-36°, ψ =4°-25°Ⅱ： φ=30°-55°, θ=144.4°-158°, ψ =4°-28° A set of experiments employing LGS （0, 150°, 22°） and （0, 90°, 0） has been performed to check the validity of the proposed calculation. The experimental relative sensitivity is in excellent agreement with the theoretical results.展开更多
In this paper,general principle of the Surface Acoustic Wave(SAW) sensor in wired and wireless con-figurations will be developed and a review of recent works concerning the field of high temperature applications will ...In this paper,general principle of the Surface Acoustic Wave(SAW) sensor in wired and wireless con-figurations will be developed and a review of recent works concerning the field of high temperature applications will be presented.The first part will be devoted to aspects of data transmission and processing.Both configurations of SAW de-vice,delay line and resonator,will be discussed as well as the remote interrogation techniques used to collect and to proc-ess signal.The second part will be devoted to the material aspects.Indeed,knowing that the conventional piezoelectric substrates such as quartz or lithium niobate cannot be used at high temperature,the choice of the material constituting the SAW device(substrate & electrodes) is one of the challenges to face.We will focus our discussion on the Langasite,the current reference for high temperature applications,and on the AlN/Sapphire structure,the very promising alternative for application where the use of high frequency is required.展开更多
Langasite(LGS,La_(3)Ga_(5)SiO_(14))is a promising material in high-temperature piezoelectric devices due to its excellent thermal stability,piezoelectricity,and electrical property.A major challenge in the development...Langasite(LGS,La_(3)Ga_(5)SiO_(14))is a promising material in high-temperature piezoelectric devices due to its excellent thermal stability,piezoelectricity,and electrical property.A major challenge in the development of LGS-based devices is to form high-strength bonding of the brittle LGS.Here,we report that the single crystal-single crystal(dual-SC)bonding of LGS is realized through thermal activation under a low com-pression of 50 kPa for the first time.A record bonding strength of 23.28 MPa is achieved within the dual-SC bonded LGS/LGS structure(with a high bonding ratio exceeding 93%),which is 5 times higher than that of the recent reported LGS/LGS bonding structure(in which a relatively fragile amorphous interface layer is formed between the two LGS samples).The smooth and void-free dual-SC bonding interface of LGS is verified via the cross-sectional transmission electron microscopy(TEM)observations.展开更多
The frequency responses of a langasite crystal microbalance （LCM） in liquid phase were investigated. It was shown that the LCM possessed much stronger oscillating ability in liquid phase than that of the commonly us...The frequency responses of a langasite crystal microbalance （LCM） in liquid phase were investigated. It was shown that the LCM possessed much stronger oscillating ability in liquid phase than that of the commonly used quartz crystal microbalance （QCM）. The frequency shifts of the LCM to the changes in mass loading, as well as viscosity and density of the liquid were measured. The LCM was applied to monitor the adsorption process of an ionic liquid film to ethanol vapor.展开更多
In this work, bulk acoustic wave propagation properties of langasite single crystal excited by lateral electric field have been investigated. Three important crystal cuts have been identified for different operational...In this work, bulk acoustic wave propagation properties of langasite single crystal excited by lateral electric field have been investigated. Three important crystal cuts have been identified for different operational modes of lateral field excitation （LFE） on langasite substrate, namely the （yxl）65° （pure-LFE mode）, （yxl）45° （quasi-LFE mode）, and （yxl）0° （pseudo-LFE mode）. Devices on langasite substrate with the above cuts were fabricated and tested, and the experimental results agree well with the theoretical analysis. It is found that a pure thickness shear mode exists in the （yxl）65° langasite LFE device with the bare side facing liquid, and no spurious mode is found due to its moderately large piezoelectric coupling factor. In addition, （yxl）0° langasite LFE device is also found suitable for liquid phase sensing applications.展开更多
Using the langasite crystal microbalance (LCM), the trends in film thickness produced by means of the chemical vapor deposition using trichlorosilane gas, monomethylsilane gas and their mixed gas were observed at 600?...Using the langasite crystal microbalance (LCM), the trends in film thickness produced by means of the chemical vapor deposition using trichlorosilane gas, monomethylsilane gas and their mixed gas were observed at 600?C and evaluated by comparison with the information from a transmission electron microscope (TEM). The crystalline silicon film thickness from trichlorosilane gas was comparable to that of an amorphous silicon carbide film from monomethylsilane gas. The film obtained from the gas mixture was amorphous and was the thinnest in this study. Because the thickness trend obtained by the LCM agreed with that by the TEM, the LCM is shown to be a convenient evaluation tool for the behavior of various film deposition.展开更多
Single crystals of Nd：La3Ga5SiO14 （NLGS） and Nd：La3Ga5.5Ta0.5O14 （NLGT） were grown by Czochralski method. Both crystals exhibit a langasite structure （space group D32 （P321） with Z = 1）, whose general formul...Single crystals of Nd：La3Ga5SiO14 （NLGS） and Nd：La3Ga5.5Ta0.5O14 （NLGT） were grown by Czochralski method. Both crystals exhibit a langasite structure （space group D32 （P321） with Z = 1）, whose general formula is A3BC2D3O14, where A, B, C and D represent the dodecahedral, octahedral and tetrahedral positions, respectively. The adding of low content of Nd does not change the crystal structure. Although they are isostructural, the distribution of atoms among the symmetric sites is different. While NLGT exhibits a perfect orderly structure, NLGS exhibits an intrinsically disordered structure due to the random distribution of Ga and Si atoms at the C3（2） symmetry sites. To understand what changes occur in the phonon distribution when Ta replaces Si, we recorded and analyzed room temperature polarized Raman spectra. We observe 8A1＋18E modes for NLGS and 10A1＋13E for NLGT crystals. When Si is substituted by Ta, we observe that the wavenumber of some modes related to vibrations involving Ga and O atoms decreases. This agrees with the fact that the Ga–O bonds are shorter in NLGS than in NLGT.展开更多
Surface acoustic wave (SAW) devices play a significant role in signal processing, frequency control and sensing applications. In general, they cannot operate at elevated temperature. The new crystal of langasite prov... Surface acoustic wave (SAW) devices play a significant role in signal processing, frequency control and sensing applications. In general, they cannot operate at elevated temperature. The new crystal of langasite provides possibility for surface acoustic wave devices applied at high temperature. This paper studies the SAW properties of single and doubly rotated cuts of LGS at high temperature. The calculated SAW properties of LGS are analyzed in space with aid of contour plots, and two promising SAW orientation regions at high temperature are presented. For some typical cuts and propagating directions within the two optimal regions, their SAW characteristics vs temperature are discussed. Based on the experimental evidence in some literatures, the reliability of calculated results is verified.展开更多
We report on the crystal-field(CF)levels of Nd^3+in Nd3CrGe3Be2O14,a representative of recently synthesized Be-containing langasites.They are the first in the family to contain two magnetic subsystems,1 D chromium and...We report on the crystal-field(CF)levels of Nd^3+in Nd3CrGe3Be2O14,a representative of recently synthesized Be-containing langasites.They are the first in the family to contain two magnetic subsystems,1 D chromium and Kagome-like rare-earth ones.High-resolution broad-band temperature-dependent spectra allow us to find all five CF Kramers doublets of the ground 4I9/2 CF multiplet and 38 levels of the excited 4I11/2,13/2,15/2,4F3/2,4F5/2+2H9/2,4F7/2+4S3/2 and 4F9/2 CF multiplets.These data form a basis for a future exploration of this interesting two-sublattice magnet with frustrated interactions.Optical transitions between Kramers doublets of Nd^3+indicate magnetic activity of 1D-chromium chains at T<20 K.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.60274062 and 10304012).
文摘The crystal langasite manifests its unique advantages and potentials for high temperature applications due to a high electromechanical coupling coefficient, temperature compensated orientations for surface acoustic wave （SAW）, and temperature stability. In order to analyze the pressure-induced frequency shift in SAW resonator type sensors at high temperature, this paper presents the electroelastic wave equations employing the effective material constants for small vibrations superimposed on biases originated from homogeneous temperature and external pressure fields in the Lagrangian description. Incorporated with the first-order perturbation integration, a model including both the mechanical and electrical perturbation items originating from thermal biases and small pressure fields is proposed. This universal model is suitable for substrate with high piezoelectricity and can be applied at either room temperature or high temperature circumstance. The criteria of optimal cuts for SAW pressure sensitivity, i.e., high electromechanical coupling coefficient and low temperature coefficient of delay, are proposed. A thorough investigation in trebly rotated cuts has shown that optimal pressure sensitive crystallographic areas can be obtained. The areas suitable for pressure sensors at room temperature are defined with Euler angles Ω1： φ=0°-0.6°, θ=144.4°-145.8°, ψ =23.2°-24.1°,Ω2： φ=59.4°-61.°, θ=34.2°-36.2°, ψ =24.1°-22.3°,Ω3： φ=119°-120°, θ=143.8°-145.5°, ψ =22.3°-23.5° The areas suitable for pressure sensors at high temperature are defined with Euler angles Ⅰ： φ=8°-30°, θ=24°-36°, ψ =4°-25°Ⅱ： φ=30°-55°, θ=144.4°-158°, ψ =4°-28° A set of experiments employing LGS （0, 150°, 22°） and （0, 90°, 0） has been performed to check the validity of the proposed calculation. The experimental relative sensitivity is in excellent agreement with the theoretical results.
基金supported by the REGION LORRAINE,Contrat Projet Etat Région 2007~2013Ple de Recherche Scientifique et Technologique.Matériaux,Energie,Procédés,Produits:Matériaux fonctionnels micro-et nanostructurés pour la réalisation de micro-et nanosystèmes."
文摘In this paper,general principle of the Surface Acoustic Wave(SAW) sensor in wired and wireless con-figurations will be developed and a review of recent works concerning the field of high temperature applications will be presented.The first part will be devoted to aspects of data transmission and processing.Both configurations of SAW de-vice,delay line and resonator,will be discussed as well as the remote interrogation techniques used to collect and to proc-ess signal.The second part will be devoted to the material aspects.Indeed,knowing that the conventional piezoelectric substrates such as quartz or lithium niobate cannot be used at high temperature,the choice of the material constituting the SAW device(substrate & electrodes) is one of the challenges to face.We will focus our discussion on the Langasite,the current reference for high temperature applications,and on the AlN/Sapphire structure,the very promising alternative for application where the use of high frequency is required.
基金the National Nat-ural Science Foundation of China(No.5207052574)the Fundamental Research Funds for the Central Universities(No.D5000220072).
文摘Langasite(LGS,La_(3)Ga_(5)SiO_(14))is a promising material in high-temperature piezoelectric devices due to its excellent thermal stability,piezoelectricity,and electrical property.A major challenge in the development of LGS-based devices is to form high-strength bonding of the brittle LGS.Here,we report that the single crystal-single crystal(dual-SC)bonding of LGS is realized through thermal activation under a low com-pression of 50 kPa for the first time.A record bonding strength of 23.28 MPa is achieved within the dual-SC bonded LGS/LGS structure(with a high bonding ratio exceeding 93%),which is 5 times higher than that of the recent reported LGS/LGS bonding structure(in which a relatively fragile amorphous interface layer is formed between the two LGS samples).The smooth and void-free dual-SC bonding interface of LGS is verified via the cross-sectional transmission electron microscopy(TEM)observations.
基金supported by the National Natural Science Foundation of China(No.20275021)the Open Foundation of the State Key Laboratory of Chemo/Biosensing and Chemometrics,Hunan University.
文摘The frequency responses of a langasite crystal microbalance （LCM） in liquid phase were investigated. It was shown that the LCM possessed much stronger oscillating ability in liquid phase than that of the commonly used quartz crystal microbalance （QCM）. The frequency shifts of the LCM to the changes in mass loading, as well as viscosity and density of the liquid were measured. The LCM was applied to monitor the adsorption process of an ionic liquid film to ethanol vapor.
基金Project supported by the National Natural Science Foundation of China(Grant No.60571014)
文摘In this work, bulk acoustic wave propagation properties of langasite single crystal excited by lateral electric field have been investigated. Three important crystal cuts have been identified for different operational modes of lateral field excitation （LFE） on langasite substrate, namely the （yxl）65° （pure-LFE mode）, （yxl）45° （quasi-LFE mode）, and （yxl）0° （pseudo-LFE mode）. Devices on langasite substrate with the above cuts were fabricated and tested, and the experimental results agree well with the theoretical analysis. It is found that a pure thickness shear mode exists in the （yxl）65° langasite LFE device with the bare side facing liquid, and no spurious mode is found due to its moderately large piezoelectric coupling factor. In addition, （yxl）0° langasite LFE device is also found suitable for liquid phase sensing applications.
文摘Using the langasite crystal microbalance (LCM), the trends in film thickness produced by means of the chemical vapor deposition using trichlorosilane gas, monomethylsilane gas and their mixed gas were observed at 600?C and evaluated by comparison with the information from a transmission electron microscope (TEM). The crystalline silicon film thickness from trichlorosilane gas was comparable to that of an amorphous silicon carbide film from monomethylsilane gas. The film obtained from the gas mixture was amorphous and was the thinnest in this study. Because the thickness trend obtained by the LCM agreed with that by the TEM, the LCM is shown to be a convenient evaluation tool for the behavior of various film deposition.
基金Supported by the Natural Science Foundation of Shandong Province(BS2015CL012,ZR2014JL029)the Higher Education and Technology Development Plan of Shandong Province(J15LA09,J14LA5)Weifang Science and Technology Development Plan(2015GX003)
文摘Single crystals of Nd：La3Ga5SiO14 （NLGS） and Nd：La3Ga5.5Ta0.5O14 （NLGT） were grown by Czochralski method. Both crystals exhibit a langasite structure （space group D32 （P321） with Z = 1）, whose general formula is A3BC2D3O14, where A, B, C and D represent the dodecahedral, octahedral and tetrahedral positions, respectively. The adding of low content of Nd does not change the crystal structure. Although they are isostructural, the distribution of atoms among the symmetric sites is different. While NLGT exhibits a perfect orderly structure, NLGS exhibits an intrinsically disordered structure due to the random distribution of Ga and Si atoms at the C3（2） symmetry sites. To understand what changes occur in the phonon distribution when Ta replaces Si, we recorded and analyzed room temperature polarized Raman spectra. We observe 8A1＋18E modes for NLGS and 10A1＋13E for NLGT crystals. When Si is substituted by Ta, we observe that the wavenumber of some modes related to vibrations involving Ga and O atoms decreases. This agrees with the fact that the Ga–O bonds are shorter in NLGS than in NLGT.
基金This work was supported by the National Natural Science Foundation of China under grant No.60274062.
文摘 Surface acoustic wave (SAW) devices play a significant role in signal processing, frequency control and sensing applications. In general, they cannot operate at elevated temperature. The new crystal of langasite provides possibility for surface acoustic wave devices applied at high temperature. This paper studies the SAW properties of single and doubly rotated cuts of LGS at high temperature. The calculated SAW properties of LGS are analyzed in space with aid of contour plots, and two promising SAW orientation regions at high temperature are presented. For some typical cuts and propagating directions within the two optimal regions, their SAW characteristics vs temperature are discussed. Based on the experimental evidence in some literatures, the reliability of calculated results is verified.
基金Project supported by the Russian Foundation for Basic Research(17-02-00603)
文摘We report on the crystal-field(CF)levels of Nd^3+in Nd3CrGe3Be2O14,a representative of recently synthesized Be-containing langasites.They are the first in the family to contain two magnetic subsystems,1 D chromium and Kagome-like rare-earth ones.High-resolution broad-band temperature-dependent spectra allow us to find all five CF Kramers doublets of the ground 4I9/2 CF multiplet and 38 levels of the excited 4I11/2,13/2,15/2,4F3/2,4F5/2+2H9/2,4F7/2+4S3/2 and 4F9/2 CF multiplets.These data form a basis for a future exploration of this interesting two-sublattice magnet with frustrated interactions.Optical transitions between Kramers doublets of Nd^3+indicate magnetic activity of 1D-chromium chains at T<20 K.
