Li2TiO3:Mn4+ Deep‐Red Phosphor for the Lifetime‐Based Luminescence Thermometry
Milićević, Bojana R.
Đorđević, Vesna R.
Brik, Mikhail G.
Srivastava, Alok M
Article (Published version)
© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Luminescence of monoclinic lithium metatitanate (Li2TiO3) powders activated with different quantities of Mn4+ is studied in detail. Its strong deep-red emission arising from the Mn4+ 2Eg → 4A2g spin forbidden transition is centered at around 688 nm and is suitable for luminescence thermometry. Structural and electron paramagnetic resonance analyses show that Mn4+ ions are equally distributed in two almost identical Ti4+ sites in which they are octahedrally coordinated by six oxygen ions. Calculations based on the exchange charge model of the crystal field provided values of Racah parameters (B=760 cm−1, C= 2993 cm−1), crystal-field splitting Dq= 2043 cm−1, and the nephelauxetic parameter β1=0.9775. The maximal quantum efficiency of 24.1% at room temperature is found for 0.126% Mn4+ concentration. Temperature quenching of emission occurs by a cross-over via 4T2 excited state of the Mn4+ ions with T1/2=262 K and is quite favorable for the application in the lifetime-based luminescence th...ermometry since relative changes in emission decay values are exceptionally-large (around 3.21% at room temperature). We derived theoretical expressions for the temperature dependence of the absolute and relative sensitivities and discuss the influence of host material properties on lifetime sensitivities. © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Keywords:crystal field / exchange charge model / luminescence thermometry / Mn4+ emission / temperature quenching of emission
Source:ChemistrySelect, 2019, 4, 24, 7067-7075
- Materials of Reduced Dimensions for Efficient Light Harvesting and Energy conversion (RS-45020)
- National Recruitment Program of High-end Foreign Experts by Chongqing University of Posts and Telecommunications (CQUPT), P.R. China [GDT20185200479]
- Joint Funds of the National Natural Science Foundation of China (NSFC) and Yunnan Province [U1702254]
- National Natural Science Foundation of China 
- Science and Technology Planning Project of Guangdong Province for Applied Science and Technology Research and Development [2017B090917001]
- Science and Technology Planning Project of Guangdong Province for Applied Science and Technology Research and Development [2016B090931007]
- Programme for the Foreign Experts [W2017011]
- Wenfeng High-end Talents Project by Chongqing University of Posts and Telecommunications (CQUPT) [W2016-01]
- Estonian Research Council grant [PUT PRG111]
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- National Recruitment Program of High-end Foreign Experts [GDT20185200479]
- National Recruitment Program of High-end Foreign Experts [GDW20145200225]