CARVALHO, R. S.; http://lattes.cnpq.br/6145935752794997; CARVALHO, Roberta Sarmento.
Resumen:
The ceramic materials are present in many applications of electronic components,
highlighting mullite and mullite-based composites. The objective of this work was to
study formulations containing aluminosilicates and alumina in order to obtain
compositions suitable for dielectric applications. Initially, the precursors kaolin, ball
clay and alumina were submitted to the characterizations: chemical, mineralogical
and granulometric, and from the chemical composition it was defined the quantity of
components in the masses. Specimens were produced ((50 mm x 15 mm x 5 mm)
(50 mm x 3 mm)) by uniaxial pressing to 19, 6 MPa. The specimens were dried at
110 oC and sintered at temperatures of 1400, 1450 and 1500 °C, with heating rate of
5 °C/min and firing level of 60 minutes. Subsequently, the specimens were submitted
to the characterizations: physicochemical, mechanical and dielectric. The relative
dielectric constant (İr) and the tangent of losses (tan į) were evaluated for the
frequencies of 0.1 kHz, 1 kHz, 10 kHz and 100 kHz at room temperature. It was
observed the majority crystallization of the mullite phase for the studied temperature
range, with morphology in the form of needles. Compositions containing higher
content of fluxes presented lower porosity (~ 1.84) and water absorption (~0.74) and
better flexural strength (~ 66 MPa). The dielectric constant values were close to
those of mullite (İr = ~ 3,5 to ~ 4,5) in the frequency of 1 kHz, for the compositions
sintered at 1400 °C. Lower dielectric losses (tan į ~ 0.01) were observed at 1400-
1500°C and 100 kHz.
