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Master's Dissertation
DOI
10.11606/D.88.1998.tde-15092010-135855
Document
Author
Full name
Caio Eduardo de Campos Tambelli
Institute/School/College
Knowledge Area
Date of Defense
Published
São Carlos, 1998
Supervisor
Committee
Gonzalez, Jose Pedro Donoso (President)
Maule, Agnieszka Joanna Pawlicka
Souza, Ernesto Chaves Pereira de
Title in Portuguese
Estudo por Ressonância Magnética Nuclear do Condutor Protônico HPb2Nb3O10. nH2O.
Keywords in Portuguese
Condutor protônico
Ressonância magnética nuclear
Abstract in Portuguese
Neste trabalho foi estudado o condutor protônico HPb2Nb3O10. nH2O , por Ressonância Magnética Nuclear pulsada do próton 'ANTPOT.1H'. Tanto o estudo da forma de linha como a relaxação spin-rede, em função da temperatura, refletem a mobilidade das espécies protônicas neste material. O início dos movimentos iônicos e moleculares produzem um forte estreitamento da largura de linha acima de 130 K. Os dados da taxa de relaxação spin-rede (1/T1) mostra um máximo entre 253 K e 273 K que depende da hidratação (n). As energias de ativação obtidas dos resultados de relaxação e largura de linha variam entre 0,14eV e 0,4eV, dependendo da hidratação. Os resultados de condutividade e RMN são consistente com um mecanismo de condução do tipo Grotthus, que consiste numa sucessão de movimentos reorientacionais e saltos de prótons. O coeficiente de difusão protônica foi estimado dos parâmetros obtidos de RMN sendo da ordem de 10-8 cm2/s. Este valor leva a uma condutividade da ordem de 10-3 S/ cm.
Title in English
Nuclear magnetic resonance study of proton conductor HPb2Nb3O10. nH2O.
Keywords in English
Nuclear magnetic resonance
Proton conductor
Abstract in English
The protonic conductor HPb2Nb3O10. nH2O , was studied by pulsed Nuclear Magnetic Resonance (NMR) of 'ANTPOT.1H'. The temperature dependence of the spin-lattice relaxation rate (1/'T IND.1') and line width, reflect the mobility of the protonic species present in this material. The onset of ionic and molecular motions produces a strong narrowing of the line at temperatures above 130 K. The spin-lattice relaxation data, obtained above 200 K, shows a maximum in 1/'T IND.1', peaking in the range 253 K to 273 K, depending on the value of n. Activation energies of protonic motions, measured from line width and relaxation data, are n dependent and lies in the range of 0,14 eV to 0,4 eV. Results of NMR and conductivity are consistent with the Grotthus conduction mechanism, consisting of a succession of molecular re-orientations and proton jumps. The protonic diffusion coefficient was estimated from the parameters obtained from NMR relaxation and found to be of the order of 10-8 cm2/s, leading to a conductivity of about 10-3 S/ cm.
 
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Publishing Date
2010-09-16
 
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