Synthesis, Crystal Structure, and Photoluminescence of Sr‐α‐SiAlON:Eu²⁺

Abstract

Sr‐containing α‐SiAlON (Srm/2Si12‐m–nAlm+nOnN16–n:Eu2+) phosphor was obtained as a major phase in compositions having small m and n values, by firing the powder mixture of SrSi2, SrO, α‐Si3N4, AlN, and Eu2O3 at 2000°C for 2 h under 1 MPa nitrogen atmosphere. The crystal structure of Sr‐α‐SiAlON was refined by the Rietveld analysis of the synchrotron X‐ray powder diffraction pattern. The crystal structure showed that the Sr–N2 bonding distance of Sr‐α‐SiAlON was fairly large compared with that of Ca‐α‐SiAlON. The displacement of N2 sites probably allow the interstices in α‐SiAlON to accommodate the introduction of the large Sr ion. Sr‐α‐SiAlON:Eu2+ phosphor has an excitation wavelength ranging from the ultraviolet region to 500 nm and emits a strong yellow light.

Synthesis, crystal structure and photoluminescence of Eu-α-SiAlON

“…6). These values are slightly smaller than that of Sr-␣-SiAlON (a = 7.79189(5) Å, c = 5.65377(2) Å) [19] in agreement with the fact that Eu 2+ is smaller than that of Sr 2+ [24]. Additionally, the lattice parameters of the sample with n = 0 in starting composition are slightly shorter than that of Sr-␣-SiAlON.…”

“…This emission band is attributable to the allowed 4f 6 5d → 4f 7 transition of Eu 2+ . Compared with Sr-␣-SiAlON:Eu 2+ ( em = 585 nm) [19], the red-shift of emission band of Eu-␣-SiAlON is expected because of the energy transfer between Eu 2+ ions and/or re-absorption of Eu 2+ at higher Eu concentration [15]. The characteristic luminescence of Eu 3+ with sharp lines between 560 nm and 630 nm is hardly observed, which is ascribed to the small Eu 3+ /Eu 2+ ratio, as expected in the nitrogen-rich environment.…”

“…A common feature of these reports is that the composition of Eu single-doped ␣-SiAlON has large m and n values. Recently, we reported the synthesis, crystal structure, and photoluminescence of Sr containing ␣-SiAlON (Sr m/2 Si 12−m−n Al m+n O n N 16−n :Eu 2+ ) phosphors having the compositions with small m and n values [19]. It clearly indicates that Sr-␣-SiAlON can be formed as the major phase in compositions with small m and n values (m = 0.70-0.80 and n = 0-0.05) [19].…”

“…Recently, we reported the synthesis, crystal structure, and photoluminescence of Sr containing ␣-SiAlON (Sr m/2 Si 12−m−n Al m+n O n N 16−n :Eu 2+ ) phosphors having the compositions with small m and n values [19]. It clearly indicates that Sr-␣-SiAlON can be formed as the major phase in compositions with small m and n values (m = 0.70-0.80 and n = 0-0.05) [19]. In the present investigation, the synthesis of Eu-␣-SiAlON with small m and n in the nominal compositions was attempted according to the routine of Sr-␣-SiAlON, due to the similarity of the ionic size between Eu 2+ and Sr 2+ .…”

Dopant Concentration Induced Optical Changes in Ca,Eu-α-Sialon

“…The optical properties of selected α-sialon:Eu 2+ samples with respect to temperatures in the range of 10 to 500 K and pressures up to 240 kbar are presented. It is well known [18,25,[38][39][40][41][42][43] that by changing the composition of α-sialon (which means changing the degree of substitution of Si-N by Al-O bonds and thus changing the environment around the Eu 2+ ions) it is possible to tune, in a certain range, the luminescence properties of Eu 2+ doped α-sialon phosphors. The main effect of high pressure is compression of the crystal, i.e., a decrease in its volume and as a consequence a decrease in interatomic distances.…”