  The effect of Sr doping in BaTiO3 (BTO) with nominal compositions
Ba0.80Sr0.20TiO3 (BSTO) have been explored in its structural, lattice
vibration, dielectric, ferroelectric and electrocaloric properties. The
temperature dependent dielectric results elucidate the enhancement in
dielectric constant and exhibit three frequency independent transitions around
335, 250 and 185 K which are related to different structural transitions. All
these transitions occur at lower temperature as compared with pristine BTO,
however; remnant electric polarization (P) of BSTO is much higher than in BTO.
The value of P is around 5 microC/cm2 at room temperature and the maximum P
around 8 microC/cm2 is observed at tetragonal to orthorhombic and orthorhombic
to rhombohedral transitions. The electro-caloric effect shows the maximum
adiabatic change in temperature deltaT approx 0.24 K at cubic to tetragonal
transition. The temperature dependent synchrotron X-ray diffraction and Raman
results shows correlations between P, crystal structure and lattice vibrations.
Our results demonstrate the enhancement in ferroelectric properties of BTO with
Sr doping. The origin of the enhancement in ferroelectric property is also
discussed which is related to the appearance of superlattice peak around room
temperature due to TiO6 octahedral distortion. These enhanced properties would
be useful to design lead free high quality ferroelectric and piezoelectric
materials.
