Phase Formation and Dielectric Characterization of the Bi2O3–TeO2 System Prepared in an Oxygen Atmosphere
Solid-state synthesis of compositions from the Bi2O3–TeO2 system show that, under an oxygen atmosphere, Te4+ oxidizes to Te6+ and yields four room-temperature stable compounds: Bi2Te2O8, Bi2TeO6, Bi6Te2O15, and new a compound with the nominal composition 7Bi2O3·2TeO2. Dense ceramics can be prepared from all these compounds by sintering between 650° and 800°C under an oxygen atmosphere. The permittivity of these compounds varies from ∼30 to ∼54, the Q×f value from 1.100 to 41.000 GHz (∼5 GHz), and the temperature coefficient of resonant frequency from −43 to −144 ppm/K. Bi6Te2O15 and 7Bi2O3·2TeO2 do not react with silver, and, therefore, they have the potential to be used for applications in low-temperature cofired ceramic (LTCC) technology.
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