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A series of Sm3+ doped phosphor Sr 2 Ga 2 GeO 7 :xSm3+ (0 = x ≤ 0.05) were synthesized for the first time to obtain red emitting component for efficient WLED device with excellent electroluminescence (EL) performance. The X-ray diffraction (XRD) analysis revealed that these powders crystalized in a tetragonal with a space group of P-421m (113) and the Sm3+ occupied the positions Sr2+ ions in the lattice of Sr 2 Ga 2 GeO 7. The germanate material Sr 2 Ga 2 GeO 7 possess a broad optical energy bandgap (E g) of 5.03 eV, which was beneficial for the charge transfer of Sm3+ to the matrix. The photoluminous (PL) properties proved that these red emitting phosphors Sr 2 Ga 2 GeO 7 :xSm3+ (0 ≤ x ≤ 0.05) exhibited two emission peaks at about 563 nm and 602 nm, which originated from the 4G 5/2 → 6H 5/2 and 4G 5/2 → 6H 7/2 transitions of Sm3+ ions under 404 nm excitation. Interestingly, when the contents of Sm3+ reached 2% mol, sample Sr 2 Ga 2 GeO 7 :0.02Sm3+ possessed a relatively best PL characterize with the CIE coordinates of (0.5386, 0.4563). Based on its good PL emission stability and decay lifetime, sample Sr 2 Ga 2 GeO 7 :0.02Sm3+ showed an excellent thermal stability with the PL emission intensity only reduced by 15.02% relative to its initial PL emission intensity when measured at 473 K. As a result, the WLED device based on phosphor Sr 2 Ga 2 GeO 7 :0.02Sm3+ presented a splendid EL performance, with a low correlated color temperature (CCT) of 4252 K, a high color rendering index (R a) of 90.6 and the CIE coordinates of (0.3701, 0.3707). • Red phosphor Sr 2 Ga 2 GeO 7 :0.02Sm3+ was first synthesized. • Sample Sr 2 Ga 2 GeO 7 :0.02Sm3+ possessed high thermal stability. • The WLED device exhibited an impressive R a of 90.6 and a low CCT of 4252 K [ABSTRACT FROM AUTHOR]

Sm3+ and Pr3+ ion co-doped phosphors Ca 3 Y 2 Ge 3 O 12 :0.04Sm3+:yPr3+ (0.001 ≤ y ≤ 0.006 mol%) were synthesized by high tempereture calcination process. The XRD results showed that samples Ca 3 Y 2 Ge 3 O 12 :0.04Sm3+:yPr3+ (0.001 ≤ y ≤ 0.006) were matched well with the standard profile Ca 3 Y 2 Ge 3 O 12 (PCSD No. 27–0092) which possessed a cubic structure with the space group I a-3d (230), and these synthesized samples exhibited irregular particles with large size of about 40 μm. The photoluminescence (PL) study demonstrated that the co-doped Pr3+ ions could improve the PL properties through the energy transition (ET) process between Pr3+ ions and Sm3+ ions, leading to a smaller liftimes of Ca 3 Y 2 Ge 3 O 12 :0.04Sm3+:0.003Pr3+ than Ca 3 Y 2 Ge 3 O 12 :0.04Sm3+. The optimum Pr3+ ions doping concentration was y = 0.003 and the CIE coordinates (0.5249, 0.4730) of Ca 3 Y 2 Ge 3 O 12 :0.04Sm3+:0.003Pr3+ lied in red light region. Notably, sample Ca 3 Y 2 Ge 3 O 12 :0.04Sm3+:0.003Pr3+ exhibited better thermal stability and larger activation energy (E a) by compariton of Ca 3 Y 2 Ge 3 O 12 :0.04Sm3+. Finally, the WLED device based on Ca 3 Y 2 Ge 3 O 12 :0.04Sm3+:0.003Pr3+, (Ba, Sr) 2 SiO 4 : Eu2+ and an ultraviolet chip of 395 nm exhibited a low correlated temperature (CCT) of 3929 K and a color rendering index (R a) of 89. Image 1 • Pr3+ can improve PL properties of Ca 3 Y 2 Ge 3 O 12 :0.04Sm3+:0.003Pr3+. • Phosphor Ca 3 Y 2 Ge 3 O 12 :0.04Sm3+:0.003Pr3+ exhibited a splendid thermal stability. • Ca 3 Y 2 Ge 3 O 12 :0.04Sm3+:0.003Pr3+ based WLED exhibited a low CCT and a high R a. [ABSTRACT FROM AUTHOR]

A series of red emitting phosphors Mg 3 Y 2-x Ge 3 O 12 :xSm3+ (0≤x ≤ 0.06) were successfully synthesized. Samples Mg 3 Y 2-x Ge 3 O 12 :Sm3+ exhibited a cubic structure pertaining to the I a-3d (230) space group and the particle sizes range from 1 μm to 5 μm. The optical properties displayed that the optimum doping concentration of Sm3+ is 4%. The phosphor Mg 3 Y 1.96 Ge 3 O 12 :0.04Sm3+ not only exhibited a broad band gap of 5.54 eV but also showed a high color purity of 97.6%. In addition, the strongest emission intensity located at 566 nm belonged to the 4G 5/2 → 6H 5/2 transition when excited at 405 nm. Thermal quenching test revealed that the sample Mg 3 Y 1.96 Ge 3 O 12 :0.04Sm3+ are excellent powders with splendid thermal stability, in which only 3.6% of the PL intensity is quenched at 473 K in comparison with that of 298 K. As a result, the W-LEDs based on Mg 3 Y 1.96 Ge 3 O 12 :0.04Sm3+ yielded a high R a of 91.1, a low CCT of 4881 K, and CIE coordinates of (0.3476, 0.3466) in a 20 mA driven current. This research work provided important guidance for the synthesis of Sm3+ doped red component with excellent luminesce properties and high thermal stability characteristics used in W-LEDs. • The phosphor Mg 3 Y 1.96 Ge 3 O 12 :0.04Sm3+ not only exhibited a broad band gap of 5.54 eV but also showed a high color purity of 97.6%. • The sample Mg 3 Y 1.96 Ge 3 O 12 :0.04Sm3+ are excellent powders with splendid thermal stability. • The W-LEDs based on Mg 3 Y 1.96 Ge 3 O 12 :0.04Sm3+ exhibited an excellent electroluminesce performance in a 20 mA driven current. [ABSTRACT FROM AUTHOR]

Two series of Eu3+ ions activated high performance red-emitting phosphors Ba 2(1-x) AGe 2 O 7 : 2xEu3+ (A = Mg, Zn, 0 ≤ x ≤ 0.2) were synthesized by high-temperature solid-state procedure. The research results showed that the host lattice Ba 2 MgGe 2 O 7 possess higher band gap than that of Ba 2 ZnGe 2 O 7 , and all the Ba 2(1-x) MgGe 2 O 7 : 2xEu3+ (BMGO: 2 xEu3+, 0 ≤ x ≤ 0.2) and Ba 2(1-x) ZnGe 2 O 7 : 2xEu3+ (BZGO: 2 xEu3+, 0 ≤ x ≤ 0.2) phosphors crystallized in a tetragonal unit cell with the space group of P 421 m (113). Compared with other phosphors in the same series, the samples BMGO: 0.30 Eu3+ and BZGO: 0.25 Eu3+ presented the highest absorption intensity when monitoring at 616 nm under 395 nm excited, respectively. Moreover, the samples BMGO: 0.30 Eu3+ and BZGO: 0.25 Eu3+ not only exhibited high color purity of 90% and 90.3%, respectively, but also possess excellent thermal stability. Unsurprisingly, the WLED devices based on BMGO: 0.30 Eu3+ and BZGO: 0.25 Eu3+ as the red-emitting components displayed good luminescence properties, especially the color rendering index (CRI, R a) R 9 represented the saturation of colour of illuminated objects exhibited a high value of 89.6 and 82.3, respectively. In contrast, the WLED device based on BMGO: 0.30 Eu3+ as red-emitting phosphors presented better electroluminescence performances than those of BZGO: 0.25 Eu3+ on account of its much favorable crystal structure, PL performance and thermal stability. Image 1 • Ba 2 AGe 2 O 7 : Eu3+ were synthesized as red-emitting phosphors. • BMGO:0.3Eu3+ and BZGO:0.25Eu3+ exhibit excellent color purity and thermal stability. • BMGO:0.3Eu3+ and BZGO:0.25Eu3+ based WLED present excellent luminescence properties. [ABSTRACT FROM AUTHOR]