DESIGN, ASSEMBLY AND CHARACTERIZATION OF COMPOSITE ...

materials within the overall structure. The following nomenclature is adopted for
referring to each material composition: BT refers to pure BaTiO3 material, Ni refers to
pure Ni material, and Ni(m) refers to a mixture of Ni and BT with BT considered as an
inclusion phase. A strategy for preparation of binary composite inks from BT and Ni
powders is described. The formulation of Ni(m) colloid inks is described in detail.
Relevant rheological properties of Ni(m) colloid inks are characterized. To assess the
parameter space where successful co-sintering may be achieved, sintering behaviors of
the Ni(m) inks and pure BT ink are investigated independently by measuring sintered
shrinkage after firing. Various temperatures profiles with peak temperature from 1200 °C
to 1350 °C are employed. Viable compositions for the Ni(m) composite ink that co-sinter
with pure BT while maintaining the ferroelectric properties of the BT and the electric
conductivity of the Ni are identified. Micro-indentation Vickers hardness tests are used to
reveal the mechanical properties of the sintered composites. Finally, example structures
in the form of a multilayer lattice and parallel bowtie stripes are printed, co-sintered, and
re-oxidized (for BT) under proper conditions.
5.2. Experimental Section
5.2.1. Materials
A Ni powder (UNP 600, Umicore, Fort Saskatchewan, Alberta, Canada) is used
as the metal phase, with manufacturer provided assay indicating a specific surface area of
1.5 m 2 /g, a particle size distribution with D10=0.862 µm, D50=1.589 µm, D90=2.85 µm, a
tap density 3.2 g/cm 3 , and 0.1% carbon, 0.005% sulfur, 0.7% oxygen by weight as
impurities. The impurities are presumed to come from surface oxide, and from
137