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Crystal-field levels of Nd3+ in a new langasite compound Nd3CrGe3Be2O14

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Journal of Rare Earths 2019年第11期37卷 1250-1254页

作者： Sergei A.Klimin Boris V.Mill Marina N.Popova Institute of Spectroscopy Russian Academy of SciencesTroitskMoscow 108840Russia Faculty of Physics M.V.Lomonosov Moscow State UniversityMoscow 119991Russia

We report on the crystal-field(CF)levels of Nd^3+in Nd3CrGe3Be2O14,a representative of recently synthesized Be-containing *** are the first in the family to contain two magnetic subsystems,1 D chromium and Kagome-like rare-earth ***-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 *** data form a basis for a future exploration of this interesting two-sublattice magnet with frustrated *** transitions between Kramers doublets of Nd^3+indicate magnetic activity of 1D-chromium chains at T<20 K.

关键词： langasite Two magnetic subsystems High-resolution spectroscopy Crystal-field levels Magnetic correlations Rare earths

Single crystal-single crystal bonding of langasite exhibited high strength of 23.28 MPa

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Journal of Materials Science & Technology 2023年第29期160卷 139-147页

作者： Guangyao Pei Binghe Ma Tao Ye Zhonggang Zhang Keli Zhao Jinjun Deng Seeram Ramakrishna Jian Luo Ministry of Education Key Laboratory of Micro/Nano Systems for Aerospace Northwestern Polytechnical UniversityXi’an 710072China Centre for Nanofibers and Nanotechnology National University of Singapore117576Singapore

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 ***,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.

关键词： Thermal activation Single crystal-single crystal bonding langasite High-strength Low compression

Growth Defects in langasite Crystals Observed with White Beam Synchrotron Radiation Topography

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Journal of Rare Earths 2006年第Z1期24卷 159-161页

作者： Wang Xuping Wang Jiyang Hu Xiaobo Zhang Jianxiu Zhao Hongyang Huang Wanxia Zhu Peiping State Key Laboratory of Crystal Materials Shandong University Jinan 250100 China State Key Laboratory of Crystal Materials Shandong University Jinan 250100 China State Key Laboratory of Crystal Materials Shandong University Jinan 250100 China State Key Laboratory of Crystal Materials Shandong University Jinan 250100 China State Key Laboratory of Crystal Materials Shandong University Jinan 250100 China Beijing Synchrotron Radiation Laboratory Institute of High Energy Physics Beijing 100039 China Beijing Synchrotron Radiation Laboratory Institute of High Energy Physics Beijing 100039 China

langasite single crystal was grown by the Czochralski method and its perfection was assessed by white beam synchrotron radiation topography. It is found that the growth core and the growth striations are the primary growth defects and they show strong X-ray kinematical contrast in the topographs. Another typical defect in LGS crystal is dislocation. The formation mechanisms of these growth defects in LGS crystals were discussed.

关键词： langasite (LGS crystal) growth striation growth core dislocation

Optimal pressure-sensitive cuts for surface acoustic waves on langasite

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Science in China(Series F) 2006年第2期49卷 254-261页

作者： HAN Tao JI Xiaojun SHI Wenkang School of Electronic Information and Electrical Engineering Shanghai Jiaotong University Shanghai200240 China

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.

关键词： surface acoustic wave langasite pressure sensitivity high temperature.

<i>In-Situ</i>Monitoring of Chemical Vapor Deposition from Trichlorosilane Gas and Monomethylsilane Gas Using langasite Crystal Microbalance

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Journal of Surface Engineered Materials and Advanced Technology 2013年第1期3卷 61-66页

作者： Hitoshi Habuka Yurie Tanaka Department of Chemical and Energy Engineering Yokohama National University Yokohama Japan.

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.

关键词： Chemical Vapor Deposition In-Situ Measurement langasite Crystal Microbalance

ADVANCES IN DESIGN,GROWTH AND APPLICATION OF PIEZOELECTRIC CRYSTALS WITH langasite STRUCTURE

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ADVANCES IN DESIGN,GROWTH AND APPLICATION OF PIEZOELECTRIC C...

Theoretical Studies on the SAW Properties of LGS at High-Temperature in Optimal Cuts

2012全国压电和声波理论及器件技术研讨会

作者： Yan-qing ZHENG Su-xian CUI Jian-jun CHEN Xiao-niu TU Jun XIN Hai-kuan KONG Er-wei SHI Shanghai Institute of Ceramics Chinese Academy of Sciences

Crystals with langasite structure consist of more than one hundred *** about 20 compounds are grown and *** this work,we first use first-principles calculation to simulate the crystal structure of 29 ordered langasite compounds and then forecast their piezoelectric related properties including dielectric constants,elastic constants,piezoelectric coefficients and electromechanical *** known ordered crystals including SNGS,STGS,CTGS,CNGS,and several novel crystals including BTGS,CTAS,CNAS were grown by Czochralski method and characterized at room temperature and at high temperature from 400 to 900℃.The experimental results of piezoelectric properties verified the validity of theoretical forecast and that errors between experimental and theoretical results were in reasonable ***-free crystals shown good prospect in application of piezoelectric sensors,combining the advantages of low cost of raw materials and high *** efforts should be paid to the growth of these novel crystals.

关键词： Piezoelectric crystals langasite Design First-principles

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Journal of Materials Science & Technology 2004年第5期20卷 512-516页

作者： Xiaojun JI, Tao HAN, Wenkang SHI and Guowei ZHANGDepartment of Instrumentation Engineering, Shanghai Jiao Tong University, Shanghai 200030, China Dept. of Instrumentation Eng. Shanghai Jiaotong Univ. Shanghai 200030 China

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.

关键词： High-temperature Surface acoustic wave langasite Optimal cuts