Biomedical Engineering Reference
In-Depth Information
no attempt has so far been made to prepare 6% Sr
2+
substituted PZT ceram-
ics with lead manganese antimony as an additional hardener dopant. h e
present work addresses this aspect. h us in the present work, a dielectric
study of the present ceramics prepared by a solid-state reaction technique
is presented and the scaling behavior of the dielectric loss spectra under-
taken to show that the distribution of relaxation times is time independent.
We will also present a careful study of the crystal structure using Rietveld
analysis and show that the material exhibits tetragonal structure with space
group P4 mm having a value of χ2 (= 2.54). A detailed temperature-depen-
dent dielectric study of the present composition has also been performed
at dif erent frequencies.
14.2 Experiment
Samples used in the present work were prepared by a modii ed solid-state
route using dif erent precursors. One of the common problems associ-
ated with the solid-state synthesis of such ceramics is the appearance of
an unwanted phase. To get rid of this unwanted phase of - stoichiometric
compositions with excess of PbO are generally used. h is naturally per-
turbs the phase stabilities because the crystal structure is very sensitive to
even small variations in the composition on account of nearly degenerate
nature of various phases. In order to bring out the intrinsic features of
the given system, it is imperative to prepare the pyrochlore-free ceram-
ics in stoichiometric compositions without using any excess of PbO. We
have achieved this by using a columbite precursor route
.
For evaluation
of purity of the chemical composition of the precipitated PbCO
3
, ther-
mogravimetric analysis (TGA) was carried out at 600 C. h e experimen-
tally observed weight loss was 16.469% for PbCO
3
.
h ermogravimetric
analysis of SrCO
3
was not carried out because of the hygroscopic
nature of SrO. Stoichiometric amounts of the PbCO
3
and SrCO
3
pow-
ders were taken for the preparation of [Pb
0.94
Sr
0.06
]CO
3
. Saturated solu-
tion of ammonium carbonate was added in the solution of PbCO
3
and
SrCO
3
in dilute nitric acid to obtain the precipitate of [Pb
0.94
Sr
0.06
]CO
3
.
h e precipitate was washed with distilled water until ammonia was com-
pletely removed and then dried in an oven. To check the formation of
[Pb
0.94
Sr
0.06
]CO
3
solid solution, X-ray dif raction data were recorded. It is
well known that the synthesis of Pb (B , B )O
3
type relaxor ferroelectrics
by calcining a stoichiometric mixture of oxides of constituent cations
generally leads to a signii cant fraction of an unwanted pyrochlore phase.
In order to prevent the formation of this unwanted phase, a columbite
