  Detailed Raman spectroscopy studies on polycrystalline Sr1-xPrxTiO3 (x=0.01,
0.025, 0.05, 0.075, 0.09, 0.13, 0.15, 0.17) samples are reported elucidating
the microscopic mechanism of relaxor ferroelectrics. The polar mode was
observed upto very high temperature ~1000 K suggesting that the dipoles exists
at temperatures well above the characteristic relaxor temperatures and they
develop a short range correlation at 505 K leading to formation of PNRs. The
TO2 polar mode showed anomalous softening in cooling below T~505 K supporting
the growth of PNRs. Fano resonance is reported in the Pr doped compounds which
decreases with increasing doping. Our work on Pr doped SrTiO3 reveals that the
local TiO6 octahedral tilt scales with the intensity of the polar mode and
hence can be used as an order parameter for relaxor transition. The study
showed that the paraelectric to relaxor ferroelectric phase transition in this
compound is random polarizability instability driven phenomenon which is
correlated with the local octahedral tilt angle. The study supports competition
and cancelation between lattice and polar instabilities at global length scale
while cooperation between the two at local length scale. The modulation in
local structure of the material in temperature interval related to dielectric
anomaly has been observed which is not been investigated previously by any
structural tool.
