Cu3TeO6 ceramics and thick films: fabrication and characterization

• Autor(a) principal: Wang, Zhonghua
• Data de Publicação: 2010
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/7360
• topic: Engenharia de materiais; Materiais cerâmicos - Propriedades dieléctricas; Sinterização; Filmes espessos; Deposição electroforética; Cerâmica electrónica

There has been an ever-growing demand for miniaturization in the electronic devices while keeping the high function density and low price. The ultimate solution is the low temperature co-firing ceramics (LTCC) technology. Targeting LTCC applications, the fabrication and dielectric properties of Cu3TeO6 thick films were studied in this thesis. The precursors were synthesized by the conventional solid state method. Copper oxide (CuO) and tellurium dioxide (TeO2) powders as starting materials with different stoichiometry were calcined at a series of temperatures. X-ray diffraction analysis of the products attest that CuTe2O5 and Cu3TeO6 were obtained as mono-phasic compounds for the CuO+2TeO2 and 3CuO+TeO2 compositions, respectively. Cu3TeO6 ceramics were well sintered at 865oC, showing a relative density of 93% and shrinkage of 29%. Sintering at higher temperature led to the decomposition of Cu3TeO6. The dielectric permittivity of the ceramics increased with the sintering temperature. The loss tangent and temperature coefficient of dielectric permittivity are very high, which do not meet the requirements of LTCC materials. Cu3TeO6 green films were fabricated by electrophoretic deposition (EPD). The thickness of green film increased rapidly with deposition time in the initial stage. The electric field exhibited a linear relationship with the thickness at fixed time. However, the quality of the films deteriorated under high voltages (>300V). Sintering of the films was carried out from 800oC to 860oC. The scanning electron microscopy (SEM) images of the film sintered at 860oC show a well densified microstructure. The Cu3TeO6 thick films exhibit poorer dielectric permittivity but lower loss tangent.