Crystal structure, defect chemistry and radio frequency relaxor characteristics of Ce-Doped SrTiO3 perovskite

- Sr(1-3x/2)CexTiO3 ceramics were prepared by using a conventional solid state method.
- Evidence of structure ordering and mixed-valence state of Ti3+/4+ ions upon Ovac formation.
- Evidence of the polar TO2 and TO4 modes and formation of polar nanoregions (PNRs).
- High-temperature relaxor behavior rather than normal ferroelectric anomalies.
- Existence of hysteresis loop and remnant polarization of ∼0.04 μC/cm2.

Crystal-defect chemistry, and temperature dependent dielectric characteristics was investigated in Ce-doped SrTiO3 (Sr(1−3/2x)CexTiO3, x = 0.45 − 0.55) ceramics. X-ray diffraction (XRD) and transmission electron microscopy (TEM) shows the evidence of structure ordering. The samples with x = 0.45 and x ≥ 0.5 display different phase structure evolution features with mixed- valence states of Ti3+/Ti4+ upon oxygen vacancy formation. The doping of Ce(x) facilitated large grain size with a dense microstructure. Activation of polar modes TO2 and TO4 indicated the evidence of polar nanoregions (PNRs). The system displays features of high-temperature frequency-dependent relaxor behavior rather than sharper frequency-independent normal ferroelectric anomalies. These relaxations were found to be bulk effect associated with singly (VO
- ) and doubly (VO
-
- ) charged oxygen vacancies.