Thesis (Ph. D.)--Auburn University. / Abstract. Vita. Includes bibliographical references (p. 70-71).

Thesis (Ph. D.)--Michigan State University. Dept. of Music Education, 2008. / Title from PDF t.p. (viewed Sept. 9, 2009). Includes bibliographical references (p. 222-223). Also issued in print.

Thesis (Ph. D.)--Florida State University, 2005. / Advisor: Dr. James S. Brooks, Florida State University, College of Arts and Sciences, Dept. of Physics. Title and description from dissertation home page (viewed Sept. 15, 2005). Document formatted into pages; contains xiii, 120 pages. Includes bibliographical references.

Thesis (Ph.D.) - University of St Andrews, January 2008.

Thesis (M.M.)--Bowling Green State University, 2006. / Document formatted into pages; contains x, 105 p. Includes bibliographical references.

Thesis (M.M.)--University of North Texas, 2006. / System requirements: Adobe Acrobat Reader. Includes bibliographical references (p. 126-130).

Dissertation (PhD) Florida State University, 2006. / Advisor: Kevin Fenton, Florida State University, College of Music. Title and description from dissertation home page (viewed 7-2-07). Document formatted into pages; contains 175 pages. Includes biographical sketch. Includes bibliographical references.

Dissertation (PhD) Florida State University, 2007. / Advisor: Kevin Fenton, Florida State University, College of Music. Title and description from dissertation home page (viewed 8-29-2007). Document formatted into pages; contains 151 pages. Includes biographical sketch. Includes bibliographical references.

REIS JÚNIOR, Daniel Valim dos. Espectroscopia Vibracional e de Impedância de A1-xA’xTaWO6.nH2O (A=H, Li, A’ = Ag,H). 2009. 121 f. Tese (Doutorado em Física) - Programa de Pós-Graduação em Física, Departamento de Física, Centro de Ciências, Universidade Federal do Ceará, Fortaleza, 2009. / Submitted by Edvander Pires (edvanderpires@gmail.com) on 2015-05-04T18:11:28Z No. of bitstreams: 1 2009_tese_dvreisjunior.pdf: 3014923 bytes, checksum: d5b180893837986bd0a9df72ba4a2d01 (MD5) / Approved for entry into archive by Edvander Pires(edvanderpires@gmail.com) on 2015-05-07T15:00:37Z (GMT) No. of bitstreams: 1 2009_tese_dvreisjunior.pdf: 3014923 bytes, checksum: d5b180893837986bd0a9df72ba4a2d01 (MD5) / Made available in DSpace on 2015-05-07T15:00:37Z (GMT). No. of bitstreams: 1 2009_tese_dvreisjunior.pdf: 3014923 bytes, checksum: d5b180893837986bd0a9df72ba4a2d01 (MD5) Previous issue date: 2009 / We have performed the characterization of doped pyrochlore (H1−xAgxTaWO6.H2O) and trirutile (Hx Li1−x TaWO6 ) samples. Raman spectroscopy and infrared transmitance thechniques were used to investigate the structural properties of doped trirutile. The studies revealed that HxLi1−xTaWO6 samples belong to the tetragonal polar symmetry P421m(D32d). Raman spectroscopy studies were also used to identify the nature of the Raman active modes of the pyrochlore materials. Among the Raman modes we can highlight the ones observed at 340 and 720 cm−1 which originate from ν4 and ν3 infrared active modes. Their presence in the Raman spectra indicates a positional disorder of the Ta and W cations. Furthermore, we studied the dependence of the frequency of these modes on the Ag+ concentration, wich revealed a monotonic decrease of the wave number with the dopant concentration x (wich was only broken for a concentration x = 0.5). Impedance spectroscopy study was performed to the electric characterization of the pyrochlore materials. The experiment consisted of measuring the dependence of the im- pedance of these system on the temperature, throughout the heating (25 to 110 o C) and the cooling (110 to 25 o C) processes. The goal was to try to avoid the humidity effect in the impedance spectra. However, for the sample with x = 0.20, we observed an anomalous response for the conductivity during the cooling process. To explain these results, we performed a microstructural characterization of the samples with x = 0.80, 0.67 and 0.20. The result is that the sample with x = 0.20 are well characterized by the model of “easy-path”, having high porosity, while the other two should have a Suzuki-type precipitate phase structure. These results explain the anomaly in the Arrehnius plot observed for the x = 0.20 concentration sample as an effect of the different microstructures. In this study we could also verify that the doped samples had a clear dependence of the activaction energies on the dopant concentration. With the exeption of the sample with concentration x = 0.20, the activation energies during the cooling process were observed to be between 0.60 and 0.23 eV, wich are the values of their pure counterparts, as reported in the literature. / Realizamos a caracterização das amostras H1−x AgxTaWO6.H2O pirocloro e Hx Li1−xTaWO6 trirrutilo. Técnicas de espectroscopia Raman e transmitância de infravermelho foram usadas com o objetivo de investigar propriedades estruturais do trirrutilo dopado. Os estudos revelaram que as amostras HxLi1−xTaWO6 pertencem ao sistema tetragonal polar P421m (D32d). Os estudos Raman serviram também para identificar a natureza dos modos Raman ativos dos materiais pirocloro. Dentre os modos Raman que podemos destacar aqueles observados a 340 e 720cm−1 que são originários dos modos infravermelho ativos ν4 e ν3. A presença destes modos indica desordem posicional dos cations Ta e W. Além disso, estudamos a dependência do número de onda destes modos com relação a concentração de Ag+, que revelou um decréscimo monotônico do número de onda com a concentração (que só foi quebrada para a concentração x = 0,5). Estudo de espectroscopia de impedância foi feito para a caracterização elétrica dos materiais pirocloros. O experimento consistiu em medidas da dependência da impedância destes sistemas com a temperatura, durante o aquecimento (25 a 110 oC), e resfriamento (110 a 25 oC). O objetivo foi tentar evitar o efeito da umidade no espectro de impedância. No entanto, para amostra com x = 0,20, obtemos uma resposta anômala da condutividade durante o resfriamento. Para explicar esse resultado, realizamos caracterização de microestrutura nessa amostra e nas amostras com x = 0,80 e 0,67. O resultado é que a amostra com x = 0,20 é bem caracterizada pelo modelo de “easy-path” por possuir elevada porosidade enquanto nas outras duas devem possuir estrutura de precipitado de fase tipo Suzuki. Estes resultados serviram para explicar porque a anomalia no gráfico de Arrehnius ocorreu somente na amostra com concentração 0,20: diferença de microestrutura. Neste estudo podemos constatar também que as amostras dopadas tiveram uma dependência das energias de ativação com relação às taxas de concentração. Com exceção da amostra com taxa de concentração 0,20, as energias de ativação no resfriamento, encontram-se entre os valores de 0,60 e 0,23 eV de suas contrapartes puras registradas na literatura.

Made available in DSpace on 2014-10-09T12:32:59Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:06:11Z (GMT). No. of bitstreams: 0 / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP