Impedance Spectroscopy and Dielectric Properties of Flash Versus Conventionally Sintered Yttria-Doped Zirconia Electroceramics Viewed at the Microstructural Level

Autor(es)

M'Peko, J. -C ^{[1, 2]} ; Francis, J. S. C. ^[2] ; Raj, Rishi ^[2]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Inst Fis Sao Carlos, Grp Crescimento Cristais & Mat Ceram, BR-13560970 Sao Paulo - Brazil

^[2] Univ Colorado, Dept Mech Engn, Boulder, CO 80309 - USA

• Tipo de documento: Artigo Científico
• Fonte: Journal of the American Ceramic Society; v. 96, n. 12, p. 3760-3767, DEC 2013.
• Citações Web of Science: 39

Resumo

The defect chemistry-modulated dielectric properties of dense yttria-doped zirconia ceramics prepared by conventional sintering (at 1350 degrees C-1500 degrees C) and electric field-assisted flash sintering (55V/cm at 900 degrees C) were studied by impedance spectroscopy. While the bulk dielectric properties from both sets of samples showed only small and insignificant changes in conductivity and permittivity, respectively, a huge increase of these properties was measured for the grain boundaries in the flash sintered specimens. A close analysis of these results suggests that flash sintering reduced grain-boundary thickness (by about 30%), while increasing the concentration of oxygen vacancies near these interfaces (by about 49%). The underlying mechanism proposed is electric field-assisted generation and accommodation of defects in the space-charge layers adjacent to the grain surface. The changes in measured permittivity are attributed to the boundary thickness effect on capacitance, while conductivity involved variations in its defect density-dependent intrinsic value, accounting for changes also observed in grain-boundary relaxation frequencies. Therefore, in terms of modifications to the specific dielectric properties of these materials, the overall consequence of flash sintering was to considerably lower the semi-blocking character of the grain boundaries. (AU)

• Processo FAPESP: 12/06448-0 - Correlação entre propriedades (di)elétricas e características (micro)estruturais em materiais termistores PTCR do tipo Ba1-x(TR)xTiO3
• Beneficiário: Jean-Claude Mpeko
• Modalidade de apoio: Bolsas no Exterior - Pesquisa