W0410
Crystal Chemistry and Crystallography of Compounds in the
Low-Temperature Cofired Ceramic (LTCC)
Bi2O3-Ag2O-Nb2O5
System. W. Wong-Ng, Q. Huang, L.P. Cook, M.D. Vaudin, I. Levin and J.
Suh, Materials Science & Engineering Laboratory, NIST, Gaithersburg, MD
20899; J.A. Kaduk, BP Amoco Chemicals, Naperville, IL 60566.
Since the early applications of low-temperature cofired
ceramic (LTCC) technology in electronic packaging more than two decades ago, the
increased use of LTCC in recent years warrants continued research in this
important area of ceramics. The
Bi2O3-Nb2O5 system is known to be
important for LTCC technology, as Ag is the metallization of choice
in many LTCC fabrications, including those with embedded (Bi,Nb)-oxides.
To understand the reactions between phases of the
Bi2O3-Nb2O5 system and Ag, a
systematic study of the phase diagram of the
Bi2O3-Ag2O-Nb2O5 system
has been conducted. In the course of this study, the crystal chemistry and
crystallography of various binary oxide phases in the
Bi2O3-Nb2O5,
Bi2O3-Ag2O, and
Ag2O-Nb2O5 systems has been reviewed and
reinvestigated. A combination of x-ray, neutron and electron powder diffraction
techniques, and differential thermal analysis/thermal gravimetric analysis
(DTA/TGA) was used to understand the crystal chemistry and crystallography of
compounds in this system. A new ternary phase with chemical formula
Bi5AgNb4O18 was also determined
(A21ma (a=5.4915(2) Å, b=5.4752(2) Å, c=24.9282(8)
Å, V= 749.52 Å3, Z=4) to belong to the family of the
Aurivillius phase,
(Bi2O2)2+(An-1BnO3n+1)2-
, which is characterized by perovskite-like
(An-1BnO3n+1)2- slabs regularly
interleaved with (Bi2O2)2+ layers.
Bi5AgNb4O18 corresponds to n=2, A=Bi, and B=
(Ag, Nb). In this talk, a discussion of the crystallography of phases
in the Bi2O3-Ag2O-Nb2O5
system and subsystems will be presented.