Download or read book Effects of Cobalt doping Oxygen reduction and Crystallographic Orientation on the Photorefractive Properties of Barium Titanate written by Jenq-Yang Chang and published by . This book was released on 1992 with total page 398 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Growth and Characterization of High Performance Photorefractive BaTiO3 Crystals written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-08 with total page 98 pages. Available in PDF, EPUB and Kindle. Book excerpt: Barium titanate has been used for many nonlinear optical applications primarily because it has high grain and high self-pumped phase conjugate reflectivities. However, barium titanate has had a relatively slow response time, and thus low sensitivity. Therefore, it has not been suited to real-time operations. In this report we will describe the modifications in crystal growth, doping, reduction, and poling that have produced barium titanate crystals with the fastest photorefractive response time reported to date, approximately 21 microseconds with a beam-coupling gain coefficient of 38.7 cm(exp -1) and the highest sensitivity reported to date of 3.44 cm(exp 3)/kJ. The sensitivity of these barium titanate crystals is comparable to or greater than other photorefractive oxides. We will show, for the first time, beam-coupling in barium titanate at video frame rates. We infer from response time measurements that barium titanate has a phonon limited mobility. Also, photorefractive response time measurements as a function of the crystallographic orientation and grating wave vector for our cobalt-doped oxygen reduced crystals indicate that their faster response time arise because of an increase in the free carrier lifetime. Warde, C. and Garrett, M. H. and Chang, J. Y. and Jenssen, H. P. and Tuller, H. L. Unspecified Center...
Download or read book Landmark Papers On Photorefractive Nonlinear Optics written by Pochi Yeh and published by World Scientific. This book was released on 1995-07-14 with total page 619 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book, intended for students, researchers and engineers, is a collection of classic papers on photorefractive nonlinear optics. Included are landmark papers on fundamental photorefractive phenomena, two-wave mixing, four-wave mixing, phase conjugators and resonators, material growth and physics, and applications in image processing, optical storage and optical computing.
Download or read book The Influence of Cobalt Doping on Deep and Shallow Trap Dependent Photorefractive Properties of Barium Titanate written by M. H. Garrett and published by . This book was released on 1992 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: The photorefractive properties of cobalt doping barium titanate have been recently reported by Rytz et al. High beam coupling gains were reported therein. Similarly, we have grown a series of cobalt doped p-type barium titanate crystals, (undoped, 17 ppm, 50 ppm and 75 ppm), that also have relatively large beam coupling gains, e.g. for Ella and k sub g//c the gain is 7.4/cm. at 514.5 nm in the 75 ppm sample. We have further characterized these crystals by determining the sublinear dependence of the response time on intensity, the asymmetry of the beam coupling gain for + or - C-axis crystal orientations, (i.e. electrooptic and absorptive coupling), intensity dependence of the gain, and light-induced dark decays. Experimental results indicate that, as the cobalt concentration is increased, the photorefractive character of the crystals change from 'type B' to 'type A' as defined by Mahgerefteh and Feinberg. Type A crystals have filled hole-shallow traps and type B crystals have partially filled hole shallow traps and thus low and high dark conductivity respectively.
Download or read book Optics Letters written by and published by . This book was released on 1992 with total page 536 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Photorefractive Effect in Barium Titanate Crystals written by A. Linz and published by . This book was released on 1988 with total page 64 pages. Available in PDF, EPUB and Kindle. Book excerpt: Variable-valent iron impurities have been suggested as the source of photorefractive charge carriers in BaTiO3. Very high-purity BaTiO3 crystals were grown with transition-metal impurity levels below the 10 to the 16th power/cc baseline estimate for photorefractivity. Iron-doped crystals also were grown with concentrations of 5, 50, 250, 500, 750, and 1000 ppm Fe. A study of some growth problems effecting purity and perfection of TSSG BaTiO3 crystals was performed. Some preliminary growth experiments in an rf heated Czochralski furnace indicated that it might be possible to utilize the cleaner growth environment of this type of equipment for BaTiO3. Studies were also conducted to investigate the problem of capping after seeding in the TSSG process. It was concluded that convective instabilities in the melt were probably the limiting factor. Keywords: Chemical purification; Crystal growth; Photorefractive effect; Iron doped; Barium titanate. (JES).
Download or read book Photorefractive and Photochromic Effects in Barium Titanate written by M. H. Garrett and published by . This book was released on 1992 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nominally undoped p-type Barium titanate was grown that exhibits interesting intensity dependent photorefractive and photochromic properties. When its photochromism is activated the absorption increases at the activating wavelength and there is a concurrent and proportional reduction in photorefractive response time. Three photoactivated and thermally reversible absorption conditions and the difference spectra of the photochromic crystal are shown in Figure 1.
Download or read book The Photorefractive Properties and Applications of Rhodium doped Barium Titanate written by Laura Anne Corner and published by . This book was released on 1999 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Optical and Photorefractive Properties of Iron doped Barium Titanate written by Ronald Scott Hathcock and published by . This book was released on 1989 with total page 386 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Enhanced Photorefractive Effects in Barium Titanate written by and published by . This book was released on 1992 with total page 51 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report documents investigations of characteristics of secondary centers (shallow traps) in BaTiO3, and the possible utilization of these traps for enhanced photorefractive effects at infrared wavelengths. Secondary centers were characterized by photo-induced absorption and two-beam coupling experiments. Two species were identified, with concentrations of approximately 1.5 x 10(exp 17) cm( -3) and 2 x 10(exp 16) cm( -3). The effect of secondary centers on the sublinear intensity dependence and temperature dependent photorefractive effects were also examined. No enhancements of photorefractive effects were also examined. No enhancements of photorefractive effects from induced population of secondary centers by external pumping were observed ... Photorefraction, Barium titanate.
Download or read book Measurements of the Microscopic Properties Contributing to Photorefraction in Barium Titanate written by Gazanfer Unal and published by . This book was released on 1986 with total page 82 pages. Available in PDF, EPUB and Kindle. Book excerpt: The photorefractive effect is a nonlinear optical phenomena that can produce phase conjugate (complex conjugate) reflection of visible light in a crystalline solid. Very little is known about the microscopic origin of photorefraction; consequently this thesis investigates the following microscopic parameters of barium titante (Barium Titante): the quantum efficiency, charge transport length and the carrier generation rate both theoretically and experimentally. BaTiO3 was chosen because it is a highly nonlinear crystal with large electrooptic coefficients and therefore, is a very efficient photorefractive material. Keywords: Phase Conjugation, Barium Titanate; Photorefraction; Crystals, Lasers.
Download or read book A Review of the Ferroelectric Properties of Barium Titanate written by John Franklin Krumwiede and published by . This book was released on 1960 with total page 126 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Synthesis and Investigation of Properties of Barium Titanate Doped with Ferromagnetic Materials for Use in Spin Field Effect Transistors written by Kapildev Kulkarni and published by . This book was released on 2004 with total page 160 pages. Available in PDF, EPUB and Kindle. Book excerpt: "The fundamental aspect of this research was to synthesize nano particles of certain materials and to investigate their properties related to potential use in spin-field effect transistor (Spin-FET). Barium titanate was doped with ferromagnetic material and nano particles of this material were synthesized using a sol-gel process. Sol-gels were characterized for their size and shape using an atomic force microscope and a scanning electron microscope. Composition of these compounds and the distribution of dopents were investigated using x-ray fluorescence and the scanning electron microscope. Dielectric properties were measured using high precision impedance, capacitance, and resistance (LCR) meter. Barium titanate, when doped with ferromagnetic materials, becomes ferroelectric material. Ferroelectric materials have finite polarization even in the absence of an applied electric field, which can be exploited for their use as source/drain in spin-FET. The sintering temperature and pH of the sol-gel solution play important roles in determining the dielectric constants, particle size and distribution of dopent in barium titanate. It was found that iron has advantage over nickel and cobalt as a dopent, as it has high electrical susceptibility"--Leaf iii.
Download or read book Studies of Photorefractive Effect in Barium Titanate written by Yeon Ho Lee and published by . This book was released on 1989 with total page 314 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Intensity Dependence Absorption and Photorefractive Effects in Barium Titanate written by G. A. Brost and published by . This book was released on 1988 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present experimental data for BaTiO3 that exhibit an intensity dependence in the absorption coefficient and the two-beam coupling coefficient at intensities between 0.002 and 40 S/sq. cm. The effective empty-trap concentration was found to increase with intensity. We present a model, in the spirt of commonly used (photorefractive) theories, for photorefraction and optical absorption that explains these effects. The intensity dependence was attributed to the presence of secondary photorefractive centers. Keywords: Barium titanates, Reprints. (MJM).
Download or read book Chemical Control of the Polymorphic Phase Boundaries in Doped Barium Titanate written by Sarah Ann Turp and published by . This book was released on 2013 with total page 450 pages. Available in PDF, EPUB and Kindle. Book excerpt: Barium titanate (BaTiO3), a known ferroelectric material, is of great interest as a future lead-free piezoelectric if appropriately doped to tailor the electric properties for specific applications. This work focuses on the study and rationalisation of the dielectric properties of a series of A-site/B-site co-doped compositions: SrZrO3-BaTiO3, CaZrO3-BaTiO3, LaScO3-BaTiO3 and GdScO3-BaTiO3. The effect of sintering conditions and microstructure on ceramics is shown to have a significant impact on the physical properties of these materials. Pellet inhomogeneity, air sensitivity in pre-calcined powders and the presence of parasitic grain boundary capacitances are all shown to have adverse effects on properties, including the magnitudes of relative permittivity and TC calculated from total capacitance data. These can be overcome by careful control of synthesis conditions. Dielectric spectroscopy measurements on the optimised materials show that increasing addition of SrZrO3, CaZrO3 or LaScO3 causes the phase transitions between the various polymorphs of BaTiO3 to coalesce. In each case TC is reduced whilst each of the other phase transitions is shifted to higher temperatures, until the coalescence temperature is reached. When doped with GdScO3 TC is observed to fall, but so too are the rhombohedral/orthorhombic and orthorhombic/tetragonal transitions, resulting in a stabilisation of the tetragonal polymorphic phase. This is suggested to result from an antipolar displacement of small Gd3+ ions, resulting in 8-coordinate ion and stabilisation of the tetragonal polymorph. The addition of dopant species is shown to result in two different high temperature conduction regimes. Both mechanisms are observed within single compositions over different temperature ranges. It is suggested that this is due to a change between n- and p-type electronic conduction processes or mixed ionic/electronic processes. Finally, it is shown that trends observed in changes to TC cannot be accounted for by simple and widely used size-based arguments alone, but requires consideration of cation size variance and charge dilution effects in order to fully understand the impact on TC of dopant addition.
