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Master's Dissertation
DOI
10.11606/D.54.1976.tde-14082014-163704
Document
Author
Full name
Jose Alberto Rodrigues Jordao
Institute/School/College
Knowledge Area
Date of Defense
Published
São Carlos, 1976
Supervisor
Title in Portuguese
Atenuação ultrassônica devido a defeitos fora do centro KC1:Cu+
Keywords in Portuguese
Atenuação ultrassônica
Defeitos fora de centro
KCl:Cu+
Abstract in Portuguese
Com base em trabalhos tanto teóricos como experimentais, concluiu-se que o Cu+ fica em posição fora de centro em alguns halogenetos alcalinos. Nesse trabalho apresentamos resultados obtidos por técnicas de ultra-som, para verificar as propriedades do dipolo elástico devido a inos Cu+ em posição fora de centro em cristais de KCl. As alturas dos picos de relaxação observados em KCl: Cu+, apresentam proporcionalidade com a concentração de defeitos e a energia de ativação foi encontrada, sendo 0.1755 e V. A partir da teoria do dipolo elástico, e das concentrações de Cu+ achados por absorção ótica, determinou-se a simetria do defeito como sendo trigonal e o fator de forma |λ1 - λ2| = (7.7 ± 0.8) 10-2. Usando valores teóricos para os deslocamentos dos 6 vizinhos (c1‾) próximos e a teoria do "elipsóide de inclusão", os momentos de dipolo elástico, λ1, λ2 e λ3 puderam ser determinados e apresentam boa concordância com o experimento. Dada a forma do pico de atenuação, comprovou-se que a reorientação dos dipolos segue o modelo clássico com um tempo de relaxação simples τo-13
Title in English
Ultrasonic attenuation due to off-center defects: KCl:Cu+
Keywords in English
KCl:Cu+
Off-center defects
Ultrasonic attenuation
Abstract in English
With basis on theoretical and work investigation it is possible to conclude that Cu+ occupies an off-center position in several alkali halides. In this work, we report some results obtained for the elastic dipole which results form an off-senter substitutional Cu+ in KCl by ultrasonic techniques. The height of the relaxation peaks observed in KCl: Cu+ are proportional to defect concentrations, and the activation energy is 0.1755 and V. From the theory for elastic dipole, and the defect concentration measured throught optical absorption and the shape factor |λ1 - λ2| = (7.7 ± 0.8) 10-2. By using theoretical values for the six nearest neighbors displacements and the "Elipsoid inclusion theory", the elastic dipole moments , λ1, λ2 e λ3 are determined. Using the shape of the attenuation peak, we conclude that the dipole reorientation follows the classical model with a single relaxation time τo-13
 
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Publishing Date
2014-08-18
 
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