Biomedical Engineering Reference
In-Depth Information
precursor route was followed here. In the present work, it was decided
to prepare precursor MnSb
2
O
6
i rst to prevent the formation of the pyro-
chlore phase. Stoichiometric amounts of Sb
2
O
5
(99% purity) and MnCO
3
(99.9% purity) were mixed with the help of mortar and pestle for 6 hours
to obtain the intimate mixture. h e room-temperature dielectric mea-
surements of these electrode pellets were done using a Hioki LCR meter.
h e XRD data on the calcined powder show that the dominant phase
is of MnSb
2
O
6
. In order to obtain the preparation of the i nal compo-
sition [Pb
0.94
Sr
0.06
] [(Mn
1/3
Sb
2/3
)
0.05
(Zr
0.495
Ti
0.505
)
0.95
]O
3
, the stoichiometric
amounts of [Pb
0.94
Sr
.06
]CO
3
, and manganese antimony (MnSb
2
O
6
), ZrO
2
(99% purity) and TiO
2
(99.5% purity) were mixed with the help of mor-
tar and pestle for 6 hours to get an intimate homogeneous mixture. h is
mixture was dried in air and then calcined at 800 C for 6 hours. h e mix-
ing of the various constituents was done using agate mortar and pestle
with acetone as the mixing media strictly for six hours for each case. Heat
treatments involving calcinations and sintering (1170 C) were carried
out with the help of a high temperature Globar furnace. In the present
work, to avoid the lead loss the pellets were sintered in PbO environment
created by lead zirconate as a spacer powder in a covered alumina cru-
cible using MgO powder as a sealing agent. h is arrangement ef ectively
reduces the lead oxide losses at higher sintering temperature. h e dura-
tion of calcinations and sintering each was kept for 6 hours. h e powder
compaction was done using a cylindrical die of 8 mm diameter and a
hydraulic press. Before cold compaction of calcined powder, a few drops
of 2% PVA solution were added to serve as a binder. For the electrical
characterizations, the sintered ceramic pellets were electrode using the
silver paste. At er applying the paste, the pellets were then dried at about
150 C in an oven. h e silver paste coated pellets were i red at 500 C for
i ve minutes. h e microstructure of sintered specimen was examined
using a scanning electron microscope.
14.3 RietveldRei nement Details
Rietveld rei nement was carried out using the XRD data with the help of
the DBWS-9411 program [8]. h e background was i tted with linear inter-
polation between a set background points with rei nable heights, while
the peak shapes were described by pseudo-Voigt proi les. In all the rei ne-
ments, scale factor, lattice parameters, positional coordinates (x,y,z) and
thermal parameters were varied. Occupancy parameters of all the ions
were kept i xed during rei nement. No correlation between the positional
