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Terahertz detectors and focal plane arrays
Published in Antoni Rogalski, Infrared and Terahertz Detectors, 2019
Improvement of pyroelectric detector’s performance can be achieved by reducing the crystal thickness and increasing the coating absorption. Most of pyroelectrics tend to lose their interesting properties as the thickness is reduced. However, some of them seem to maintain their properties better than others. This seems particularly true for lithium tantalate oxide (LiTaO3) and related materials. New material-processing techniques such as ion milling and ion slicing have made available LiTaO3 and lithium niobate oxide (LiNO3) materials with thickness of less than 10 μm. Using the new thin-film materials, we have seen current responsivity values higher than 4 μA W−1, resulting in hybrid detector optical amplifier performance of less than 1.0 × 10−10 WHz−1/2 [118]. Thin-film LiTaO3 pyroelectric detectors are now commercially available. However their absorption in the terahertz range remains a challenge. Some promising developments are expected in the area of single- and multiwall-CNT (SCNT and MCNT, respectively) coatings for pyroelectric detectors. Table 28.6 and Figure 28.31 characterize LiTaO3 THz pyroelectric detector—Model SPH-62 THz fabricated by Spectrum Detector Inc. [119].
Piezoelectric Devices
Published in Kenji Uchino, Ferroelectric Devices, 2018
Various materials are currently being used for SAW devices. The most popular single-crystal SAW materials are lithium niobate and lithium tantalate. The materials have different properties depending on the cut of the material and the direction of propagation. The fundamental parameters considered when choosing a material for a given device applications are SAW velocity, temperature coefficients of delay (TCD), electromechanical coupling factor, and propagation loss. SAWs can be generated and detected by spatially periodic, interdigital electrodes on the plane surface of a piezoelectric plate. A periodic electric field is produced when an RF source is connected to the electrode, thus permitting piezoelectric coupling to a traveling surface wave. If an RF source with a frequency, f, is applied to the electrode having periodicity, d, energy conversion from an electrical to mechanical form will be maximum when () f=f0=vs/d,
Electro-Optical Scanners
Published in Gerald F. Marshall, Glenn E. Stutz, Handbook of Optical and Laser Scanning, 2018
Timothy K. Deis, Daniel D. Stancil, Carl E. Conti
Lithium niobate (LiNbO3) and lithium tantalate (LiTaO3) are the most common perovskite materials in use. For reasons of producibility and quality, they are typically grown to be slightly lithium-rich—this is referred to as congruently grown niobate or tantalate. These congruent materials exhibit Curie temperatures of 1470 and 890 K, respectively, giving them stable EO properties at room temperature or slightly elevated temperatures. They are also commercially available with fairly consistent properties across several vendors.
Analysis of generated shear wave due to stress discontinuity in a monoclinic layered structure
Published in Waves in Random and Complex Media, 2021
Shalini Saha, Abhishek Kumar Singh, Mriganka Shekhar Chaki
Among anisotropic materials, monoclinic are the one having single plane of symmetry with 13 elastic constants, much higher than that of the idealistic isotropic material. The monoclinic materials are found in abundance inside Earth's crust as crystal or other material. Materials such as Y-cut quartz, Lithium tantalate, and Lithium niobate exhibit monoclinic symmetry, hence are good examples of monoclinic media. It is an important fact that among all other crystalline forms such as trigonal, hexagonal, tetragonal, orthorhombic, monoclinic, and triclinic, the monoclinic material exist in maximum stable state. These inherent properties of the monoclinic material encourage us to undertake the current study. Numerous researchers [6–9] have presented results on the wave propagation and reflection problems in the monoclinic medium.
Dispersion and absorption study of SH waves in sinusoidally corrugated heterogeneous viscoelastic layer sandwiched between heterogeneous isotropic half-space and magnetoelastic monoclinic half-space
Published in Waves in Random and Complex Media, 2021
During an earthquake, the seismic waves generated propagate through the different structures of the Earth. These structures which are composed of different materials has a substantial amount of influence on the wave propagation. Monoclinic materials have been known to be found in good quantities below the Earth and have a sizeable amount of influence on wave propagation. Therefore, it becomes obligatory to study such materials which possess some remarkable characteristics and has a substantial amount of contribution to the wave propagation. Quartz, lithium tantalate and lithium niobate are good examples of monoclinic materials. Monoclinic materials are especially found to exist in sedimentary rocks such as sandstone and shale, carbonate rocks, gneiss, quartzite, and other metamorphic rocks. Some distinguishable works by authors on the monoclinic medium are Kalyani et al. [19], Chattopadhyay and Choudhury [20], Singh and Khurana [21], and Singh et al. [22].
Study of pyrolysis kinetics and characterization using TG-FTIR, GC, and BET using high ash Indian sub-bituminous coal
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2019
Ashok Prabhakar, Anup Kumar Sadhukhan, Roni Mallick, Parthapratim Gupta
The thermogravimetric analyzer (STA 6000, Perkin Elmer) was used for the experimental investigation for the pyrolysis of coal. The analyzer has top loading balance design with balance resolution of 0.1 µg and a temperature accuracy of ± 0.5 °C. The sample mass of approximately 5 mg was placed in open cylindrical alumina crucibles (180 µl). The inert gas (N2) of 40 ml/min was used for the purging of an internal system. The pyrolysis investigation was performed using the heating rate of 10°C, 20°C, and 30°C /min. The volatile fractions obtained during the coal pyrolysis were analyzed by an in-line FTIR analyzer (Spectrum Two, Perkin Elmer) through the coupled transfer line maintained at 250°C (Perkin Elmer, TG-IR interface, TL 8000). The cell path-length of 100 mm and infrared gas cell volume of 11.3 cm3 with KBr windows were used. The gas cell was equipped with MIR (LiTaO3-lithium tantalate) detector. The FTIR analysis was performed in the band range of 4000–400 cm−1 region with a resolution of 0.5 cm−1. The analysis of FTIR was performed considering the existing reference spectra in the public spectrum libraries of NIST (NIST Chemistry Webbook 2006).