Biomedical Engineering Reference
In-Depth Information
pure compound gives better insulation properties than an earlier report by
Jun
et al.
, where activation energy was only 0.58 eV. h is result is similar to
the result obtained in the case of Nb-doped BiFeO3 and a BiFeO
3
-BaTiO
3
solid solution [100]. h is increase in resistance might be explained by the
increase in grain boundary resistance, which mainly contributes to the total
resistance. h is result is also supported by the homogeneous and spherical
grain size, which is much smaller than that obtained previously.
From the Figure 13.21, it is clear that when Bi
3+
ion is substituted in low
concentration (x=0.1) of La
3+
ion, the curve shows almost linear behavior as
the pure compound at high temperature. An increase in La
3+
ion concentra-
tion from x=0.1 to x=0.2 and x=0.3 increases the resistivity and activation
energy more with respect to x=0.1. Further increase in La
3+
ion concentra-
tion from x=0.3 to x=0.4 and x=0.5, is responsible for more increase in the
resistivity and their activation energies. All the compounds of La-doped
BiFeO
3
show almost similar behavior. h e increase in resistivity as well as in
activation energy may be explained on the basis of dif erent bond energies
of Bi-O and La-O bond in the compound. h e higher bond energy of La-O
bond (799kJ/mol) in comparison to bond energy of Bi-O bond (337kJ/mol)
is responsible for an increase in activation energy and enhancement in resis-
tivity of La-substituted compounds. h e variation of activation energies of all
the compounds with concentration (x) are shown in Table 13.5.
13.5 Magnetic Properties
13.5.1 Introduction
h e term magnetism comes from the ancient Greek city of Magnesia,
where many natural magnets were found. We now refer to these natural
Table 13.5
Variation of activation energy with La
concentration.
S.No.
Bi
1-x
La
x
FeO
3
Ea (eV)
1
x=0.0
0.814
2
x=0.1
0.817
3
x=0.2
0.820
4
x=0.3
0.878
5
x=0.4
1.012
6
x=0.5
1.135
