Li2TiO3:Mn4+ Deep‐Red Phosphor for the Lifetime‐Based Luminescence Thermometry. Issue 24 (24th June 2019)

• Record Type: Journal Article
• Authors: Dramićanin, Miroslav D.; Milićević, Bojana; Đorđević, Vesna; Ristić, Zoran; Zhou, Jianbang; Milivojević, Dušan; Papan, Jelena; Brik, Mikhail G.; Ma, Chong‐Geng; Srivastava, Alok M.; Wu, Mingmei
• Is Part Of: ChemistrySelect. Volume 4:Issue 24(2019)
• Page Start: 7067
• Page End: 7075
• Publication Date: 2019-06-24
• Subjects: crystal field -- exchange charge model -- luminescence thermometry -- Mn4+ emission -- temperature quenching of emission; Chemistry -- Periodicals; 540.5
• DOI: 10.1002/slct.201901590
• Languages: English
• ISSNs: 2365-6549

Abstract

Abstract: Luminescence of monoclinic lithium metatitanate (Li2 TiO3 ) powders activated with different quantities of Mn 4+ is studied in detail. Its strong deep‐red emission arising from the Mn 4+ 2 Eg → 4 A2g 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 β1 =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 T2 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. Abstract : The luminescence of Mn 4+ activated Li2 TiO3 deep‐red phosphor provides the high‐performance temperature sensing with temperature resolution better than 30 mK over the wide temperature range. The engineering of the Mn 4+ activated materials for the high‐precision luminescence thermometry via the control of the energies of 4 T2g level and phonon coupling is shown.