Framework oxides with the capacity to host mobile interstitial oxide anions are of interest as electrolytes in intermediate temperature solid oxide fuel cells (SOFCs). High performance materials of this type are currently limited to the anisotropic oxyapatite and melilite structure types. The langasite structure is based on a corner-shared tetrahedral network similar to that in melilite but is three-dimensionally connected by additional octahedral sites that bridge the layers by corner sharing. Using low-temperature synthesis, we introduce interstitial oxide charge carriers into the LaGa Ge O langasites, attaining a higher defect content than reported in the lower dimensional oxyapatite and melilite systems in LaGaGeO ( = 1.5). Neutron diffraction and multinuclear solid state O and Ga NMR, supported by DFT calculations, show that the excess oxygen is accommodated by the formation of a (Ge,Ga)O structural unit, formed from a pair of edge-sharing five-coordinated Ga/Ge square-based pyramidal sites bridged by the interstitial oxide and a strongly displaced framework oxide. This leads to more substantial local deformations of the structure than observed in the interstitial-doped melilite, enabled by the octahedral site whose primary coordination environment is little changed by formation of the pair of square-based pyramids from the originally tetrahedral sites. AC impedance spectroscopy on spark plasma sintered pellets showed that, despite its higher interstitial oxide content, the ionic conductivity of the LaGa Ge O langasite family is lower than that of the corresponding melilites La Sr GaO. The cooperative structural relaxation that forms the interstitial-based (Ga,Ge)O units stabilizes higher defect concentrations than the single-site GaO trigonal bipyramids found in melilite but effectively traps the charge carriers. This highlights the importance of controlling local structural relaxation in the design of new framework electrolytes and suggests that the propensity of a framework to form extended units around defects will influence its ability to generate high mobility interstitial carriers.
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http://dx.doi.org/10.1021/acs.chemmater.9b01734 | DOI Listing |
Nanomaterials (Basel)
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Institute of Physics, Polish Academy of Sciences, 02-668 Warsaw, Poland.
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Department of Urology, Ewha Womans University College of Medicine, Seoul, Korea.
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View Article and Find Full Text PDFBiochim Biophys Acta Mol Basis Dis
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Department of Pediatric Nephrology and Rheumatism and Immunology, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, Shandong 250021, China; Department of Pediatric Nephrology and Rheumatism and Immunology, Shandong Provincial Hospital, Cheeloo College of Medicine, Shandong University, Jinan, Shandong 250021, China. Electronic address:
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View Article and Find Full Text PDFAntioxidants (Basel)
December 2024
Department of Pneumology, Medical University of Lodz, 90-419 Lodz, Poland.
The aging process significantly impacts lung physiology and is a major risk factor for chronic respiratory diseases, including chronic obstructive pulmonary disease (COPD), idiopathic pulmonary fibrosis (IPF), asthma, and non-IPF interstitial lung fibrosis. This narrative clinical review explores the molecular and biochemical hallmarks of aging, such as oxidative stress, telomere attrition, genomic instability, epigenetic modifications, proteostasis loss, and impaired macroautophagy, and their roles in lung senescence. Central to this process are senescent cells, which, through the senescence-associated secretory phenotype (SASP), contribute to chronic inflammation and tissue dysfunction.
View Article and Find Full Text PDFSmall
January 2025
Key Laboratory of Biorheological Science and Technology, Ministry of Education, College of Bioengineering, Chongqing University, No. 174 Shazheng Road, Chongqing, 400044, China.
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