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Li 2 TiO 3 :Mn 4+ Deep‐Red Phosphor for the Lifetime‐Based Luminescence Thermometry
Author(s) -
Dramićanin Miroslav D.,
Milićević Bojana,
Đorđević Vesna,
Ristić Zoran,
Zhou Jianbang,
Milivojević Dušan,
Papan Jelena,
Brik Mikhail G.,
Ma ChongGeng,
Srivastava Alok M.,
Wu Mingmei
Publication year - 2019
Publication title -
chemistryselect
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.437
H-Index - 34
ISSN - 2365-6549
DOI - 10.1002/slct.201901590
Subject(s) - luminescence , phosphor , excited state , ion , analytical chemistry (journal) , electron paramagnetic resonance , monoclinic crystal system , quenching (fluorescence) , crystal (programming language) , materials science , chemistry , lithium (medication) , atomic physics , crystal structure , fluorescence , nuclear magnetic resonance , crystallography , physics , optics , optoelectronics , chromatography , medicine , programming language , organic chemistry , computer science , endocrinology
Luminescence of monoclinic lithium metatitanate (Li 2 TiO 3 ) powders activated with different quantities of Mn 4+ is studied in detail. Its strong deep‐red emission arising from the Mn 4+ 2 E g → 4 A 2g spin forbidden transition is centered at around 688 nm and is suitable for luminescence thermometry. Structural and electron paramagnetic resonance analyses show that Mn 4+ ions are equally distributed in two almost identical Ti 4+ 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 β 1 =0.9775. The maximal quantum efficiency of 24.1% at room temperature is found for 0.126% Mn 4+ concentration. Temperature quenching of emission occurs by a cross‐over via 4 T 2 excited state of the Mn 4+ ions with T 1/2 =262 K and is quite favorable for the application in the lifetime‐based luminescence thermometry 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.