Overlapping large polaron tunnelling in lanthanum silicate oxyapatite.

Autor: Yadav A; Department of Physics, Indian Institute of Technology (Banaras Hindu University) Varanasi, Varanasi 221005, India., Jha PA; Department of Physics, Indian Institute of Technology (Banaras Hindu University) Varanasi, Varanasi 221005, India., Jha PK; Department of Physics, Indian Institute of Technology (Banaras Hindu University) Varanasi, Varanasi 221005, India., Jha N; Department of Physics, Institute of Chemical Technology Mumbai 400019, India., Singh P; Department of Physics, Indian Institute of Technology (Banaras Hindu University) Varanasi, Varanasi 221005, India.
Jazyk: angličtina
Zdroj: Journal of physics. Condensed matter : an Institute of Physics journal [J Phys Condens Matter] 2022 Dec 28; Vol. 35 (9). Date of Electronic Publication: 2022 Dec 28.
DOI: 10.1088/1361-648X/acad53
Abstrakt: Amongst the various fast ion conductors, lanthanum excess lanthanum silicate oxyapatite (La10-α(SiO 4 ) 6 O2+δ) has shown higher oxide ion conductivity with lower activation energy. On the other hand, the activation energy increases with La vacancies (La at 4f site). In the present work, La site is altered with Ca to form (La1-xCa x ) 9.67 (SiO 4 ) 6 O2+δ(x=0.0,0.05,0.10and 0.15) with minimum oxygen non-stoichiometry and studied the hopping/tunnelling mechanism with the Ca substitution. The elemental content obtained from Rietveld refinement of the x-ray diffractograms suggests La deficiency with minimum oxygen deficiency. Further, XPS and TGA studies confirm the formation of La deficient samples. Temperature and frequency dependent ac conductivity in the temperature range (548-973 K) suggests that the conduction takes place via overlapping large polaron tunnelling. Further, the tunnelling distance and polaron radii as a function of temperature and frequency are observed to be altered with Ca and affecting the ion conducting channel through the elongation of La(6 h) triangles. Our study suggests the phononic contribution play a pivotal role in ionic transport.
(© 2022 IOP Publishing Ltd.)
Databáze: MEDLINE
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