Structural evolution induced by substitution of designated molybdate sites (MoO4−2) with different anionic groups (BO3−3, PO4−3 and SO4−2) in CaMoO4:Sm3+ phosphors-A study on color tunable luminescent properties

Near‐ultraviolet light–induced dazzling red emission in CaGd2(MoO4)4:2xSm3+ compounds for phosphor‐converted WLEDs

“…As shown in Figure B, the measured emission spectrum contained four bands with the central wavelengths of approximately 563 nm ( 4 G 5/2 → 6 H 5/2 ), 600 nm ( 4 G 5/2 → 6 H 7/2 ), 645 nm ( 4 G 5/2 → 6 H 9/2 ), and 706 nm ( 4 G 5/2 → 6 H 11/2 ) originating from the 4f‐4f transitions of Sm 3+ ions . On the basis of previous literatures, ones knows that the 4 G 5/2 → 6 H 5/2 transition pertains to the magnetic dipole transition, while the 4 G 5/2 → 6 H 9/2 is related to the electric dipole transition . In general, the emission intensity ratio of electric dipole transition to magnetic dipole transition can be applied to identify the symmetry properties of the local environment surrounding the trivalent rare‐earth ions.…”

“…Obviously, the monitored spectrum contained a broad absorption peak in the short wavelength range which was ascribed to the charger transfer (CT) transition of O 2− → Mo 6+ in the MoO 4 2− group. Aside from the CT band, four sharp absorption peaks located at 405 nm ( 6 H 5/2 → 4 I 13/2 ), 420 nm ( 6 H 5/2 → 4 G 9/2 ), 440 nm ( 6 H 5/2 → 4 I 15/2 ), and 480 nm ( 6 H 5/2 → 4 I 9/2 ), which were attributed to the featured absorption of Sm 3+ ions, were also recognized in the diffuse reflectance spectrum. Besides, there is relation between the optical band gap ( E g ) and the absorption factor ( α ), as demonstrated below:here hv denotes the phonon energy, n = 1/2, 2, 3/2, and 3 shows the direct, allowed indirect, forbidden direct, and forbidden indirect electron transition, respectively, and A refers to the coefficient.…”

“…As disclosed, the recorded excitation spectrum can be divided into two parts, that is, a broad excitation band and several narrow excitation peaks. In special, the broad excitation band in the range of 225‐350 was assigned to the charge transfer (CT) band arising from the transition of O 2− → Mo 6+ in the MoO 4 2− group, whereas the remanent peaks centered at around 365, 378, 405, 420, 440, and 480 nm were ascribed to the transitions of 6 H 5/2 → 4 D 3/2 , 6 H 5/2 → 4 P 7/2 , 6 H 5/2 → 4 L 3/2 , 6 H 5/2 → 4 G 9/2 , 6 H 5/2 → 4 I 15/2 , and 6 H 5/2 → 4 I 9/2 , respectively . Compared with other excitation peaks, the band located at approximately 405 nm, which belongs to the NUV region, had the strongest intensity, demonstrating that the studied samples can be excited by the NUV light.…”

Environment-Dependent Eu2+-Activated Ba3CaK(PO4)3 toward White-Light Emission by Chemical Cosubstitution of the (BO3)3– Anion Group

“…Meanwhile, Dai et al reported that the formation energy of cation sites occupied by Eu 2+ may decrease with a huge distortion generated by the substitution of (PO 4 ) 3– and (BO 3 ) 3– , resulting in a new luminescence center . Typically, this approach is not restricted by the conditions of similar structures and space groups, and the luminescence performance of Eu 2+ at different lattice positions will be intensively influenced by the huge distortion induced by the substitution for (BO 3 ) 3– and (PO 4 ) 3– . − Therefore, cosubstitution can be a promising method to achieve white emission doped with a single Eu 2+ because of its flexibility and effectiveness.…”