Photo Curing and Pressureless Sintering of Orange-emitting Glass-ceramics

doi:10.15541/jim20210518

Abstract

Abstract:

Because of low thermal conductivity and weak physical and chemical stabilities, traditional “phosphor in silicone” color converters are precluded from high-power white LED applications. All-inorganic bulk luminescence materials not only can circumvent organic encapsulation, but also have higher thermal conductivity. However, those bulk materials are high in cost and very difficult to be shaped into three-dimensional structures. Here, based on amorphous silica nanoparticles, a slurry, containing (Gd,Y)AG:Ce phosphor powders and can be polymerized under UV light, were developed. Bulk (Gd,Y)AG:Ce-silica glass composites were prepared successfully through photo curing, debinding in air and pressureless sintering. Under excitation of blue light, these luminescence glass-ceramics exhibit broadband orange emission peaking at 575 nm with internal quantum efficiency higher than 90%. Our results show that the interfacial reaction between (Gd,Y)AG:Ce and silica glass is very weak, and thus the former can be well embedded into bulk silica glass. Such all-inorganic color converters were further used to fabricate high-power warm white LEDs with correlated color temperature smaller than 4500 K, color rendering index higher than 75, and luminous efficiency of 74 lm·W ^-1. Luminescence saturation threshold of the as-fabricated laser lighting device is as high as 2.84 W·mm^-2, where its luminous flux can achieve 180 lm. Moreover, preparation of (Gd,Y)AG: Ce-silica glass composites is compatible to 3D printing technology, thus allowing the mass manufacturing of color converters with complex 3D structures, which may promote personalization and modularization of high-power white LEDs.

Key words: glass-ceramics, phosphors, warm white light, 3D printing

CLC Number:

TQ174

LI Qi, HUANG Yi, QIAN Bin, XU Beibei, CHEN Liying, XIAO Wenge, QIU Jianrong. Photo Curing and Pressureless Sintering of Orange-emitting Glass-ceramics[J]. Journal of Inorganic Materials, 2022, 37(3): 289-296.

Figures/Tables 7

Fig. 1 Photographs, transmittance spectra, and XRD patterns of (Gd,Y)AG:Ce-PiG (a) (Gd,Y)AG:Ce-PiG (0.5 mm in thickness) with different doping concentrations under daylight and blue light (using a 480 nm filter to filter out blue light when taking pictures); (b) Transmittance spectra of (Gd,Y)AG:Ce-PiG samples; (c) XRD patterns of silica glass, (Gd,Y)AG:Ce phosphors and (Gd,Y)AG:Ce-PiG Colorful figures are availuable on the website

Fig. 2 Optical photos and EDS images of 3% (mass fraction) (Gd,Y)AG:Ce-PiG (a) Fluorescence microscope image; (b, c) 2D and 3D confocal laser scanning microscope images; (d) SEM image; (e, f) EDS spectra of Si and Al

Fig. 3 Luminous performance of (Gd,Y)AG:Ce-PiG (a) Excitation and emission spectra of 5% (mass fraction) (Gd,Y)AG:Ce-PiG; (b) Values of internal quantum efficiency (IQE), absorption efficiency (AE) and external quantum efficiency (EQE) of (Gd,Y)AG:Ce-PiG with different doping concentrations; (c) Temperature-dependent emission spectrum of 5% (mass fraction) (Gd,Y)AG:Ce-PiG PiG; (d) Temperature dependences of integrated emission intensity of (Gd,Y)AG:Ce-PiG and (Gd,Y)AG:Ce phosphor

Fig. 4 Electroluminescence spectra and their corresponding CIE color coordinates of white LEDs (a) Electroluminescence spectra; (b) Corresponding CIE color coordinates. White LEDs fabricated by using (Gd,Y)AG:Ce-PiG (0.8 mm in thickness) with different doping concentrations under the current of 100 mA; The inset shows the picture of LED device

Table 1 Optical performance of the packaged white LED devices

Concentration (mass fraction)	Luminous efficiency/(lm·W^-1)	CCT/K	CRI
3%	70.7	5717	84.1
5%	74.2	4444	78.4
7%	81.9	3398	67.7
9%	72.9	2907	60.5

Fig. 5 Optical performance of (Gd,Y) AG:Ce-PiG under high power (a) Schematic of reflective LD device; (b) Luminous flux of (Gd,Y)AG:Ce-PiG (0.8 mm in thickness) with different doping concentrations as a function of the laser power density; (c) Emission spectra of 5% (mass fraction) (Gd,Y)AG:Ce-PiG under different laser powers densities; (d) Values of CCT, CRI and luminous efficacy of radiation (LER) of 5% (mass fraction) (Gd,Y)AG:Ce-PiG under different laser power densities Colorful figures are availuable on the website

Fig. 6 3D printed fluorescence converter (a) Photos of 5% (mass fraction) doped 3D printed precursor; (b) Photos of sintered (Gd,Y)AG:Ce-PiG; (c) Sintered (Gd,Y)AG:Ce-PiG under 450 nm blue light irradiation; (d) Device demonstration of white LED when combined with blue LED chip

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