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Quasi-two-dimensional magnets with triangular motifs in the structure
Published in A.N. Vasiliev, O.S. Volkova, E.A. Zvereva, M.M. Markina, Low-Dimensional Magnetism, 2019
A.N. Vasiliev, O.S. Volkova, E.A. Zvereva, M.M. Markina
Most of the compounds of the langasite family have the structure of Ca3Ga4Ge2O14, shown in Fig. 7.20: the trigonal lattice with the space symmetry group P321 [363, 364]. There are two layers in the langasite structure: the z = 0 layer formed by large oxygen polyhedra, and the z = 1/2 layer with two types of oxygen tetrahedra. In each layer there are two types of polyhedra, only four positions for cations: a Thompson cube and an octahedron in the z = 0 layer, large and small tetrahedra in the z = 1/2 layer. These sites for cations can be occupied by four different ions, or the same cation can be located in polyhedra of different types. The general formula is written as A3BC3D2O14, where the letters A, B, C and D denote four different positions. In order to organize a frustrated exchange interaction in langasites, one should create substances in which magnetic ions are placed in structural positions A and/or D, which form kagomes and triangular sublattices, respectively, as shown in the right panel of Fig. 7.20.
Passive Radio-Frequency Acoustic Sensors and Systems for Wired and Wireless Applications
Published in Vikas Choudhary, Krzysztof Iniewski, MEMS, 2017
Sylvain Ballandras, Gilles Martin, Jean-Michel Friedt, Victor Plessky, Virginie Blondeau-Pâtissier, William Daniau, Thomas Baron, Luc Chommeloux, Stéphane Tourette, Jean-François Leguen, Bruno François, Christophe Droit, Meddy Vanotti, Marc Lamothe, David Rabus, Nicolas Chrétien, Emile Carry
Langasite [15] was studied in the early 1980s as a substitute for quartz with various specific advantages: a low phase velocity yielding more compact IF devices than on quartz and a higher electromechanical coupling favorable to increase the filter relative to the bandwidth. This material presents the crystal orientations for which Rayleigh-like waves can be temperature-compensated and therefore presents significant assets to make quartz out of its place. However, this material is far from meeting quartz industrial maturity, but high-temperature (above 500°C) applications sound particularly accessible for it as it does not suffer from any Curie effect (crystal symmetry change), allowing to make it operable up to 1100°C (in theory, but 900°C has already been achieved experimentally [16]).
Dispersion Relations Of Saw Propagating Under Periodical Gratingon Langasite
Published in Amir Hussain, Mirjana Ivanovic, Electronics, Communications and Networks IV, 2015
Xiaolan Qian, Fangqian Xu*, Yixiang Chen, Xuelan Zou, Zhenfei Zhao
The features of the piezoelectric langasite (LGS), such as high electromechanical coupling coefficients, the existence of temperature compensated cuts, and the absence ence of temperature compensated cuts, and the absence about 1400∘C, make it a desirable piezoelectric substrate about 1400∘C, make it a desirable piezoelectric substrate for BAW and SAW devices and sensors (Weihnacht et al. 2012, Naumenko 2011, Naumenko 2012, Kenny 2006)
Use of Surface Acoustic Wave (SAW) for Thermal Conductivity Sensing of Gases – a Review
Published in IETE Technical Review, 2021
Fahim Durani, Upendra Mittal, Jitender Kumar, A.T. Nimal
The choice of substrate material is crucial from sensitivity point of view. Researchers have explored different types of piezoelectric materials and crystal cuts. Most commonly used substrates are YX-cut quartz, ST quartz, YZ – LiNbO3 and 128° YX LiNbO3. Among them ST-cut quartz has least sensitivity towards temperature. It has zero Temperature coefficient of Frequency (TCF) at room temperature and is seldom used for temperature sensing. YX-cut quartz, on the other hand, has much better sensitivity towards temperature and has been used for temperature sensing in certain cases, particularly in wireless temperature sensing, due to high Q factor [64]. Most widely used substrate material, however, are YZ- LiNbO3 and 128° YX LiNbO3. Both materials are highly sensitive for temperature with LiNbO3/YZ cut having the maximum temperature sensitivity [65,66]. Table 2 shows the sensitivity for different materials [60]. A special substrate material worth mentioning here is Langasite. The material is used for high temperature sensing applications (up to 1400°C) [67]. Langasite devices are developed using platinum and palladium IDTs. For thermal conductivity-based sensing, YZ- LiNbO3 and 128° YX LiNbO3 are, however, the most appropriate substrate materials.