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The fluorescent ceramic GdAG:Ce was formed by aqueous tape casting-isostatic pressing process and synthesized by high temperature solid state method. To investigate the effect of introduction of Gd3+ on the crystal structure, the photoluminescence (PL) properties, decay lifetime and the white light-emitting diodes (WLED) applications, non-Gd3+ analogue sample YAG:Ce was prepared as well. In contrast, fluorescent ceramic GdAG:Ce exhibited a relatively smaller XRD peaks, much stronger PL emission intensity and shorter lifetime than that of YAG:Ce. These findings could be beneficial to the improvement of the WLED performance. Moreover, fluorescent ceramic GdAG:Ce was made up of practical with garnet structure, which possessed good thermal stability. As a consequence, an increase of color rendering index (Ra) to 62.3 and decrease of correlated temperature (CCT) to 3208 K was achieved by the WLED device based on fluorescent ceramic GdAG:Ce. The impressive results provided a basis for the fluorescent ceramic used in the field of WLED with high Ra and low CCT. [ABSTRACT FROM AUTHOR]

Eu3+-doped germanate based red emitting phosphors SrGe4O9: xEu3+ (0 ≤ x ≤ 0.5 mol%) were prepared by high-temperature solid-state procedure. Moreover, the Density Functional Theory (DFT) calculation, X-ray diffraction (XRD) Rietveld refinement, scanning electron microscopy (SEM), and photoluminescence (PL) measurement were discussed in detail to fully investigate the crystal structure and PL properties of SrGe4O9: xEu3+. Furthermore, the Judd–Ofelt (J–O) analysis demonstrated that the Eu3+ ions in the SrGe4O9 host possessed lower sites symmetry. In addition, the phosphor SrGe4O9: 0.35%Eu3+ displayed superior thermal stability with PL intensity at 423 K is around 90% of its initial value at 298 K. As a result, the white light emitting diodes (WLED) device based on SrGe4O9: 0.35%Eu3+ achieved an expected result of a correlated color temperature (CCT) of 4573 K and a color rendering index (CRI) of 80.8 under a voltage of 3 V and a driven current of 20 mA. [ABSTRACT FROM AUTHOR]

Abstract Novel BaGe 4 O 9 :Eu3+ red-emitting phosphors were synthesized by a high-temperature solid-state reaction. The crystal structures, morphological properties, elements analysis, optical properties and fluorescence decay time were investigated systematically. In contrast, the optimal Eu3+-doping concentration is 30 mol% when monitored at 591 nm with a 394 nm excitation. The energy transfer of Eu3+ ions in BaGe 4 O 9 host lattice is dominated by the exchange interaction with the critical distance (R c) of 5.28 Å. As expected, the red-emitting phosphor BaGe 3.7 O 9 :0.3Eu3+ exhibited a better quantum yield (QY) of 57.9% and an excellent lifetime of 2.25 ms. Consequently, the red-emitting phosphors BaGe 3.7 O 9 :0.3Eu3+ revealed a promising performance in warm WLED device with the CIE coordinates of (0.4365, 0.4130), the color temperature (T c) of 3079 K and the color rendering index (R a) of 85.8 under a driven current of 20 mA. These results indicate that the BaGe 4 O 9 :Eu3+ phosphors are prospective candidates as red-light component for warm white light-emitting diodes (WLEDs) devices. Graphical abstract Novel BaGe 4 O 9 :Eu3+ red-emitting phosphors for warm light-emitting diodes were synthesized by a high-temperature solid-state reaction. Image 1 Highlights • Novel BaGe 4 O 9 :Eu3+ red-emitting phosphors were synthesized by a high-temperature solid-state reaction. • The BaGe 4 O 9 :Eu3+ phosphors are prospective candidates as red-light component for warm white light-emitting diodes devices. [ABSTRACT FROM AUTHOR]