A closer look at the defects and luminescence of nanocrystalline fluorides synthesized via ionic liquids: the case of Ce3+-doped BaF2

Sharma, R.K.; Chouryal, Y.N.; Slesarev, A.I.; Ivanovskikh, K.V.; Leonidov, I.I.; Nigam, S.; Ghosh, P.

Авторы: Sharma Rahul Kumar, Chouryal Yogendra Nath, Slesarev Anatoly I., Ivanovskikh Konstantin V., Leonidov Ivan I., Nigam Sandeep, Ghosh Pushpal
Журнал: New Journal of Chemistry
Том: 44
Номер: 1
Год издания: 2020
Издательство: Royal Society of Chemistry
Местоположение издательства: United Kingdom
Первая страница: 200
Последняя страница: 209
DOI: 10.1039/c9nj04526k
Аннотация: Phase pure BaF2 doped with Ce3+ (0.1%) nanocrystals are synthesized using an ionic liquid (IL) ([C4mim][BF4]) assisted solvothermal method where the IL is not only used as a reaction medium and a capping agent, but also as a reaction partner. Subsequently, upon calcining the as-prepared nanocrystals at various temperatures (200, 400, 600 and 800 °C), athough the crystal phase remains the same, however, a significant change in the lattice strain and morphology is observed. Tensile strain appears in the nanocrystals calcined at temperatures up to 400 °C, but a reversal of the strain, i.e. compressive strain, takes place when calcination is performed at 600 °C and onwards. Nanoflakes are obtained until calcination at 400 °C. However on calcination at 600 °C and beyond, a drastic modification in the morphology is observed. Layer or step-like structures appear due to secondary nucleation of nanoparticles. Meanwhile, the photoluminescence (PL) intensity of Ce3+ ions gradually decreases with the calcination temperature and finally vanishes at 600 °C/800 °C. To investigate the reasons for the quenching of the PL intensity, thermally stimulated luminescence (TSL) and thermally stimulated exoelectron emission (TSEE) measurements are performed. The TSL and TSEE results indicate that in addition to the domination of deeper electron traps that appear as a high-temperature shift of TSEE glow peaks for both 600 °C and 800 °C, some new types of defects like F vacancies (F-centers) can be present, especially in the 800 °C calcined sample. The conditions leading to the quenching of Ce3+ luminescence in the nanoparticles are analyzed and discussed.
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A closer look at the defects and luminescence of nanocrystalline fluorides synthesized via ionic liquids: the case of Ce3+-doped BaF2статья

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