LITAO3 Characterization of Rubidium on Temperature Variations (original) (raw)
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Optical Properties of LiTaO3 Thin films crystallized by RTA processes
Journal of Electroceramics, 2006
High-performance pyroelectric infrared detectors have been fabricated using Lithium tantalite (LiTaO 3) thin films deposited on Pt(111)/Ti/SiO 2 /Si(100) substrates by diol-based sol-gel method and rapid thermal annealing (RTA) technique. The dielectric and pyroelectric properties of IR detectors of LiTaO 3 thin films crystallized by conventional and RTA processes are investigated. Experimental results reveal that the heating rate will influence strongly on dielectricity and pyroelectricity of LiTaO 3 thin films. The voltage responsivities (Rv) measured at 80 Hz increase from 5496 to 8455 V/W and the specific detecivities (D *) measured at 300 Hz increase from 1.94 × 10 8 to 2.38 × 10 8 cmHz 1/2 /W with an increase of heating rate from 600 to 1800 • C/min. However, the voltage responsivity and the specific detecivity decrease with heating rate in excess of 1800 • C/min. The results show that the LiTaO 3 thin film detector with a heating rate of 1800 • C/min exists both the maximums of voltage responsivity and specific detecivity.
Effects of Membrane Thickness on the Pyroelectric Properties of LiTaO 3 Thin Film IR Detectors
High-performance pyroelectric infrared (IR) detectors have been fabricated using lithium tantalite (LiTaO 3 ) thin films deposited on Pt(111)/Ti/SiO 2 /Si(100) substrates by the diol-based sol-gel method. The thermal isolation of detecting elements was achieved by anisotropic wet etching of the back of the silicon substrate. In order to reduce the thermal mass and thermal time constant of the detector, the sensing element was fabricated on a thin membrane. The effects of membrane thickness on the response of pyroelectric IR detectors were studied by changing the membrane thickness (20-350 mm). As the membrane thickness decreased, the voltage responsivity (R v ) increased from 4300 up to 8398 V/W, and the specific detectivity (D Ã ) also increased from 1:2 Â 10 8 to 2:7 Â 10 8 cmÁHz 1=2 /W. Experimental results reveal that the thermally isolated detectors with membrane thickness of 20 mm exhibit excellent sensitivity.
Ferroelectrics, 2007
We present temperature dependences of pyroelectric response in LiNbO 3 and LiTaO 3 single crystals in operating condition as pyroelectric detectors and in the range 4,2-400 K. In the range 200-400 K, the pyroelectric response is nearly constant. At low-temperature (40-80 K) the pyroelectric response is shown to be the largest. In the range 4,5-12 K, the sign of the pyroelectric coefficient is found to change. This could be used for temperature stabilization devices.
Recent developments in ferroelectrics for infrared detectors
Physica Status Solidi (a), 1980
The requirements for a material to be useful in a pyroelectric infrared detector or thermal imaging system are summarised and the properties of several of the more commonly used pyroelectrics are reviewed. An account is given of the development and properties of a new pyroelectric ceramic in the uranium-doped PbZr0,-PbTi0,-Pb,FeNb06 system for use in single-element pyroelectric detectors. This is contrasted with an account of the growth and characterisation of the improper ferroelectrics FeI and NiBr boracite single crystals for use as pyroelectric vidicon target materials. Die Anforderungen an ein Material, das als pyroelektrischer Mrarotdetektor oder in einem Bildwandler Verwendung finden soll, werden zusammengestellt, und die Eigenschaften einiger gebriiuchlicher F'yroelektrika werden angegeben. ttber Entwicklung und Eigenschaften eines neuen pyroelektrischen Keramikmaterials aus dem urandotierten System PbZr0,-PbTi0,-Pb,FeNbO, wird berichtet, das in pyroelektrischen Detektoreinzelelementen verwendet werden kann. Dem werden Einkristalle BUS FeI-und NiBr-Borazit gegeniiber gestellt, beides uneigentliche Ferroelektrika, und iiber deren Kristallzucht, Charakterisierung und Verwendung als pyroelektrisches Material fur Vidikontargets wird berichtet.
Dielectric and pyroelectric properties of LiTaO3:P(VDF-TrFE) composite films
2009
Pyroelectric infrared radiation detectors are one of kind thermal sensors, operating at ambient temperature, unlike semiconductor detectors, which require cooling. They also have a uniform spectral response in a wide range of wavelengths, including the main band of infrared transmission of the earth's atmosphere. Recently, 0-3 composites consisting of ferroelectric ceramic particles dispersed in a ferroelectric polymer have stimulated interest due to their good mechanical flexibility and strength, and excellent piezoelectric and pyroelectric properties. Lithium tantalite [(LiTaO3), LT] ceramic particles have been incorporated into a polyvinylidene fluoride-trifluoroethylene [P(VDF-TrFE) 70/30 mol%] copolymer matrix to form composite films. The films were prepared using solvent casting method with the LT powder homogeneously dispersed in the P(VDF-TrFE) copolymer matrix with various volume fractions. Electrical properties such as the dielectric constant, dielectric loss, and pyr...
Sensors and Actuators A: Physical, 2014
Polymer-ceramic nanocomposites with good pyroelectric properties are proposed as promising materials for the detection and measurement of thermal waves, including infrared radiation. They possess simultaneously the advantages of high detection sensitivity of the ceramic as well as the flexibility and light weight of the polymer. Selection of the appropriate ceramic additive and the polymer matrix is the key to the success for the development of the best material for any application. The aim of this work is to develop highly sensitive, at the same time flexible, polymer-nanocomposites for pyroelectric detector applications by dispersing the well known pyroelectric material, lithium tantalate, LiTaO 3 , in nanocrystalline form, in an inherently pyroelectric host polymer matrix, polyvinylidene difluoride (PVDF). LiTaO 3 nanoparticles are synthesised and dispersed in PVDF at varying volume fractions, and composite materials cast in the form of films for measurements. The -phase of PVDF is confirmed from powder XRD, FT-IR and DSC measurements. The dielectric properties, shore D hardness and pyroelectric coefficients of the cast films are measured. The thermal conductivity and specific heat capacity of the films are measured following a photothermal technique. From these data the pyroelctric figures of merit of the composite films have been determined and values compared with that of pure PVDF film. It is found that, in general, the pyroelectric figure of merit increases with concentration of LiTaO 3 ; however, it is at the expense of mechanical flexibility of the material. This paper aims at providing guidelines to strike the right balance between detection sensitivity and material flexibility (or mouldability), depending on the application.
Influence of chemical reduction on optical and electrical properties of LiTaO3 crystal
Journal of Alloys and Compounds, 2010
Reduced lithium tantalate (LiTaO 3 , LT) wafers were prepared by chemically reducing regular congruent LT wafers in mixed iron and lithium carbonate powders under a flowing nitrogen atmosphere. The electrical conductivity, Curie temperature, infrared spectrum, UV-vis transmittance, piezoelectric constants and dielectric properties of the LT wafers before and after reduction were measured. In comparison with regular LT wafers, it was found that both the electrical conductivity and the optical absorption in the visible region are greatly increased after reduction, which is beneficial for eliminating pyroelectric discharge and for high accuracy device processing. In addition, we also found that the piezoelectric and dielectric properties of the chemically reduced wafers remain almost the same, a prerequisite for fabricating SAW devices. The effects of mechanisms related to chemical reduction on the evolution of the physical properties of LT wafers are also discussed.
Self-Polarized Pyroelectric LiTaO3 thin films
We present a characterization study to develop selfpolarized, highly pyroelectric lithium tantalate thin films obtained by RF magnetron sputtering. A preliminary work is done on the bottom electrode to reduce short-term variations of the pyroelectric behavior. Then, the influence of pressure and of deposition temperature is studied to determine the best set of parameters as to obtain a large pyroelectric behavior. The crystalline structure modification as well as the influence on the pyroelectric coefficient have been studied in each case. An asdeposited pyroelectric coefficient as high as 32 µC.m -2 .K -1 has been obtained for the optimal set of pressure (2 mTorr) and temperature (630 °C).