Processing and Dielectric Properties of Sillenite Compounds Bi 12 MO 20−δ (M = Si, Ge, Ti, Pb, Mn, B 1/2 P 1/2 )

Six sillenite compounds Bi 12 MO 20‐δ (M = Si, Ge, Ti, Pb, Mn, B 1/2 P 1/2 ) were synthesized, and the resulting single‐phase powders were then sintered to obtain ∼97% dense ceramics. An analysis of their microwave dielectric properties, performed at ∼5.5 GHz, revealed a permittivity of ∼40 for all six compounds. The temperature coefficient of resonant frequency was the lowest for the Pb analogue (−84 ppm/K) and was found to increase with increasing ionic radius of the B‐site ion to a value of −20 ppm/K for the Bi 12 SiO 20 and Bi 12 (B 1/2 P 1/2 )O 20 compounds. The Q × f value is a maximum for Bi 12 SiO 20 and Bi 12 GeO 20 with 8100 and 7800 GHz, respectively. The dielectric properties of the sillenites have been correlated with the structure of the oxygen network of the sillenite crystal lattice. As a result of its low sintering temperature (850°C), chemical compatibility with silver, low dielectric losses, and temperature‐stable permittivity, the Bi 12 SiO 20 compound is a suitable material for applications in low‐temperature cofiring ceramic (LTCC) technology.