Raman spectroscopic investigation of relaxor behavior in Pr doped SrTiO3 and Origin of Fano resonance

TL;DR

This study uses Raman spectroscopy to explore the microscopic mechanisms of relaxor behavior in Pr-doped SrTiO3, revealing the role of local structural distortions, polar nanoregions, and Fano resonance in phase transitions.

Contribution

It provides new insights into the local structural dynamics and the origin of relaxor ferroelectricity in Pr-doped SrTiO3, highlighting the significance of octahedral tilt and Fano resonance.

Findings

Polar mode persists up to ~1000 K, indicating high-temperature dipole presence.

Formation of polar nanoregions occurs around 505 K, supported by mode softening.

Fano resonance decreases with increased Pr doping, linking local structure to relaxor behavior.

Abstract

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.