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Abstract Luminescence mechanism of self-activated phosphor Ca 0.75 Sr 0.2 Mg 1.05 Si 2 O 6 (CSMS) originating from oxygen vacancy defects has been deeply investigated by regulating synthesis temperature. The results demonstrate that the luminescence comes from three different oxygen defects in the crystal structure. For Ce3+ doped CSMS (ICSD#68180), two concentration quenching phenomena can be observed at x = 0.03 and 0.12 as the result of the formation of new substance CaMgSi 2 O 6 (ICSD#17043), which leads to the actual concentration of Ce3+in CSMS (ICSD#68180) is far less than the doping concentration since part of Ce3+ ions enter CaMgSi 2 O 6 (ICSD#17043). The emission spectra of CSMS: x Ce3+ shifts from 388 nm to 405 nm with increasing Ce3+ content, which mainly should be due to the 5d energy center of Ce3+ shifting down and the crystal field split. Graphical abstracts fx1 [ABSTRACT FROM AUTHOR]

A series of Na 1-z K z Ba 1-y Sr y B 9 O 15 :Eu2+ were synthesized by the high temperature solid state method. H 3 BO 3 excess makes it easier for Eu2+ to enter Na+ site, and the single-phase "blue + green" double emission band can be observed, which is proved by thermoluminescence and the change of crystal structure. Moreover, there exists an intense energy transfer from the blue-emitting center to the green-emitting center, which is proved by the decay curve. The occupation of Eu2+ can be tuned by the introduction of Sr2+ and K+ in NaBaB 9 O 15. Further, the highly thermal-sensitive property of NaBaB 9 O 15 : 1%Eu2+ makes it feasible for its potential application in luminescent ratiometric thermometers with wide temperature range. In addition, the disorder degree of matrix cations increases with the incorporation of K+, which improves the thermal stability. Image 1 • Eu2+ can enter into Na+ site with the excessive H 3 BO 3 and muti-band emission is achieved. • Sr2+/K+ can adjust the occupied radio of Eu2+ in Ba2+ and Na+ site. • K+ can improve the thermal stability of NBB:Eu2+ due to the disorder degree of matrix cations. • NBB:1%Eu2+ could be a versatile solid-state probe. [ABSTRACT FROM AUTHOR]