Thermal Quenching of Luminescence in a Disordered Compound: EuNa2Mg2 (  VO 4 ) 3

Abstract

Luminescence of EuNa2Mg2false(VO4)3 is six times as bright as that of YVO4:normalEu under 365 nm light excitation at room temperature, but it suffers from thermal quenching at higher temperatures. The quenching is mainly caused by non‐radiative relaxation from the emitting states. Energy diffusion among the lowest excited states, 5D0 , to sinks is a main reason of relatively weak quenching below 500°K. At higher temperatures, drastic quenching due to nonradiative relaxation within each Eu3+ ion is observed. Disordered distribution of Eu3+and Na+ revealed by optical and powder x‐ray diffraction measurements is considered to induce the thermal quenching. Similar strong quenching beginning at around 500°–600°K is observed also for other disordered compounds, EuK5false(MoO4)4 and normalEuAfalse(MoO4)2 false(A=normalNa,K,normaland Rbfalse) .

The luminescence spectroscopy and thermal stability of red-emitting phosphor Ca9Eu(VO4)7

“…For example, the disordered distribution of Eu 3+ and Na + in EuNa 2 Mg 2 (VO 4 ) 3 was also considered to induce the thermal quenching. Similar strong quenching was also observed in other disordered compounds, such as EuK 5 (MoO 4 ) 4 and EuA(-MoO 4 ) 2 (A = Na, K, and Rb) [13]. Consequently, the selection of the host materials and the fundamental understanding of energy transfer within phosphors are important.…”

“…We have clearly illustrated that this broad excitation (200-350 nm) was due to the absorption of VO 4 3À group in Ca 9 Dy(VO 4 ) 7 host [13]. This indicates that the transfer energy can be taken place efficiently from the VO 4 3À to Eu 3+ ions in Ca 9 Eu(VO 4 ) 7 .…”

“…This structure characteristic can be suggested to be responsible for the strong luminescence and stable thermal quenching in Ca 9 Eu(VO 4 ) 7 . Yamamoto et al [13] have suggested that the disordered distribution of Eu 3+ in a concentrated Eu-compound is responsible for the thermal quenching. For example, the strong quenching of luminescence were observed in EuNa 2 Mg 2 (VO 4 ) 3 , EuK 5 (MoO 4 ) 4 and EuA(MoO 4 ) 2 (A = Na, K and Rb) [13].…”

“…Yamamoto et al [13] have suggested that the disordered distribution of Eu 3+ in a concentrated Eu-compound is responsible for the thermal quenching. For example, the strong quenching of luminescence were observed in EuNa 2 Mg 2 (VO 4 ) 3 , EuK 5 (MoO 4 ) 4 and EuA(MoO 4 ) 2 (A = Na, K and Rb) [13]. The knowledge of the site-distribution over the different sites in a host structure will be useful to deeply analyze the luminescence mechanisms [25].…”

“…For example, Setlur et al [12] have reported that the red luminescence of Eu 3+ doped Ca 2 NaMg 2 V 3 O 12 can provide a high-quality white emission spectrum from the single phosphor. And Yamamoto et al have reported that the luminescence of EuNa 2 Mg 2 (VO 4 ) 3 is six times as bright as that of YVO 4 :Eu 3+ under 365 nm light excitation at room temperature [13]. However, they all suffer from thermal quenching at higher temperatures.…”