Article: Computational prediction and experimental confirmation of rhombohedral structures in Bi₁.₅CdM₁.₅O₇ (M = Nb, Ta) pyrochlores
RSC advances. 2017 Mar. 09, v. 7, no. 26
2017
Abstract: In this study, computationally predicted band gaps and structures using density functional theory (DFT) in Bi₁.₅CdM₁.₅O₇ (M = Nb, Ta) pyrochlores are confirmed by experimental data on synthesized samples. Ordered Cd substitutions in the B-site of the ... ...
| Abstract | In this study, computationally predicted band gaps and structures using density functional theory (DFT) in Bi₁.₅CdM₁.₅O₇ (M = Nb, Ta) pyrochlores are confirmed by experimental data on synthesized samples. Ordered Cd substitutions in the B-site of the pyrochlore structures are required to achieve electronic band gaps in the calculated energy band structures, when using full plane waves for DFT calculations, which are supported by a significantly lower total enthalpy. The computationally predicted band gap values are closely matched to experimental band gaps estimated from optical absorption spectra in the UV-Vis. In addition to the prediction of electronic structures, the models also indicate that the large ionic radius of the Cd-cation leads to symmetry modification from the archetypal cubic pyrochlore structure in Bi₁.₅CdM₁.₅O₇ (M = Nb, Ta). A rhombohedral structure and localized superlattice order are confirmed using X-ray diffraction (XRD) and transmission electron microscopy (TEM) analysis. Energy dispersive X-ray spectroscopy profiles across the superlattice domain interfaces, which are constant within experimental uncertainty, indicate that domain formation is not compositionally driven but likely a mechanism to alleviate strain build up. Raman and FTIR spectroscopy analyses on these two compounds display strong similarities suggesting that peaks and activities belong to the same structure type. |
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| Keywords | Fourier transform infrared spectroscopy ; Raman spectroscopy ; X-ray diffraction ; cadmium ; density functional theory ; energy-dispersive X-ray analysis ; enthalpy ; models ; prediction ; spectral analysis ; transmission electron microscopy ; uncertainty |
| Language | English |
| Dates of publication | 2017-0309 |
| Size | p. 15632-15643. |
| Publishing place | The Royal Society of Chemistry |
| Document type | Article |
| ISSN | 2046-2069 |
| DOI | 10.1039/c6ra27633d |
| Database | NAL-Catalogue (AGRICOLA) |
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