Photoluminescence detection of symmetry transformations in low-dimensional ferroelectric ABO 3 perovskites

• Published in: Journal of materials chemistry. C, Materials for optical and electronic devices Materials for optical and electronic devices, 2020-08, Vol.8 (31), p.10767-10773
• Main Authors: Ofoegbuna, Tochukwu, Bajgiran, Khashayar R., Kizilkaya, Orhan, Thomson, Stuart A. J., Melvin, Adam T., Dorman, James A.
• Format: Article
• Language: English
• ISSN: 2050-7526; 2050-7534
• DOI: 10.1039/D0TC01183E

Symmetry-dependent properties such as ferroelectricity are suppressed at room temperature in Pb-free ABO 3 perovskites due to antiferrodistortive dynamics (octahedral rotations/tilts), resulting in the preferential stabilization of centrosymmetric crystals. For this reason, defect engineering (Ca doping, oxygen vacancy, etc. ) has been leveraged to break the symmetry of these crystals by inducing symmetry/structural transitions to modify the local A/B-site environment. This work demonstrates the use of in situ / ex situ photoluminescence spectroscopy to systematically detect symmetry/structural transformations in prototypical ferroelectric ABO 3 perovskites. These baseline optical responses are compared to recently synthesized Ca x Sr 1−x NbO 3 (CSNO) nanocrystals, which undergoes similar ferroelectric/structural phase transitions. Furthermore, the resultant PL response is corroborated with X-ray diffraction (XRD) and absorption spectroscopy (XAS) measurements to confirm the structural changes. This ability to directly monitor the local site symmetry within ABO 3 perovskites via photoluminescence spectroscopy can be used to screen for temperature- and defect-induced ferroelectric transitions.