Disentangling octahedral distortion and symmetry breaking in the ordered double perovskite SrLaCoNbO6
Abstract
We report a comprehensive high temperature structural investigation of the B-site ordered double perovskite SrLaCoNbO6 using combined Raman spectroscopy and x-ray diffraction (XRD) over the range 25--900~∘C. Two distinct temperature-driven anomalies are identified at TOD = 300± 25 ∘C and TPT = 750± 25 ∘C through pronounced renormalizations in the phonon frequency and linewidth, accompanied by the evolution and suppression of characteristic XRD reflections. The low-temperature anomaly at TOD is associated with an isostructural octahedral distortion within the monoclinic P21/n phase. At TOD, the radial and angular distortion parameters of the CoO6 and NbO6 octahedra decrease to near-zero values before reversing upon further heating due to an inversion of the in-plane Co--O and Nb--O bond-length hierarchy. The high-temperature anomaly at TPT corresponds to a symmetry-breaking structural phase transition from P21/n to the monoclinic I2/m phase, confirmed by group-theoretical analysis and Rietveld refinement. These results demonstrate that integrating temperature-dependent Raman spectroscopy with laboratory-based XRD, complemented by quantitative octahedral distortion analysis, provides a robust approach to disentangle isostructural octahedral distortions from symmetry-breaking phase transitions in complex double perovskite oxides without recourse to synchrotron or neutron diffraction facilities.
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BibTeX
@misc{kumar2026disentangling,
title = {{Disentangling octahedral distortion and symmetry breaking in the ordered double perovskite SrLaCoNbO$_6$}},
author = {Ajay Kumar and Clemens Ulrich and Yaroslav Mudryk and Rajendra S. Dhaka},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.37835},
eprint = {2609.37835},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.37835},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Disentangling octahedral distortion and symmetry breaking in the ordered double perovskite SrLaCoNbO_6
AU - Ajay Kumar
AU - Clemens Ulrich
AU - Yaroslav Mudryk
AU - Rajendra S. Dhaka
PY - 2026
DA - 2026/09/29
PB - arXiv
DO - 10.48550/arxiv.2609.37835
UR - https://arxiv.org/abs/2609.37835
AB - We report a comprehensive high temperature structural investigation of the B-site ordered double perovskite SrLaCoNbO_6 using combined Raman spectroscopy and x-ray diffraction (XRD) over the range 25--900~^∘C. Two distinct temperature-driven anomalies are identified at T_OD = 300± 25 ^∘C and T_PT = 750± 25 ^∘C through pronounced renormalizations in the phonon frequency and linewidth, accompanied by the evolution and suppression of characteristic XRD reflections. The low-temperature anomaly at T_OD is associated with an isostructural octahedral distortion within the monoclinic P2_1/n phase. At T_OD, the radial and angular distortion parameters of the CoO_6 and NbO_6 octahedra decrease to near-zero values before reversing upon further heating due to an inversion of the in-plane Co--O and Nb--O bond-length hierarchy. The high-temperature anomaly at T_PT corresponds to a symmetry-breaking structural phase transition from P2_1/n to the monoclinic I2/m phase, confirmed by group-theoretical analysis and Rietveld refinement. These results demonstrate that integrating temperature-dependent Raman spectroscopy with laboratory-based XRD, complemented by quantitative octahedral distortion analysis, provides a robust approach to disentangle isostructural octahedral distortions from symmetry-breaking phase transitions in complex double perovskite oxides without recourse to synchrotron or neutron diffraction facilities.
ER -