scholarly journals Thermally stable and highly efficient red-emitting Eu3+-doped Cs3GdGe3O9 phosphors for WLEDs: non-concentration quenching and negative thermal expansion

2021 ◽  
Vol 10 (1) ◽  
Author(s):  
Peipei Dang ◽  
Guogang Li ◽  
Xiaohan Yun ◽  
Qianqian Zhang ◽  
Dongjie Liu ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Thermal Expansion ◽  
White Light ◽  
Coefficient Of Thermal Expansion ◽  
Internal Quantum Efficiency ◽  
Negative Thermal Expansion ◽  
Concentration Quenching ◽  
Excellent Thermal Stability ◽  
Red Phosphor ◽  
Highly Efficient

AbstractRed phosphor materials play a key role in improving the lighting and backlit display quality of phosphor-converted white light-emitting diodes (pc-WLEDs). However, the development of a red phosphor with simultaneous high efficiency, excellent thermal stability and high colour purity is still a challenge. In this work, unique non-concentration quenching in solid-solution Cs3Gd1 − xGe3O9:xEu3+ (CGGO:xEu3+) (x = 0.1–1.0) phosphors is successfully developed to achieve a highly efficient red-emitting Cs3EuGe3O9 (CEGO) phosphor. Under the optimal 464 nm blue light excitation, CEGO shows a strong red emission at 611 nm with a high colour purity of 95.07% and a high internal quantum efficiency of 94%. Impressively, this red-emitting CEGO phosphor exhibits a better thermal stability at higher temperatures (175–250 °C, >90%) than typical red K2SiF6:Mn4+ and Y2O3:Eu3+ phosphors, and has a remarkable volumetric negative thermal expansion (coefficient of thermal expansion, α = −5.06 × 10−5/°C, 25–250 °C). By employing this red CEGO phosphor, a fabricated pc-WLED emits warm white light with colour coordinates (0.364, 0.383), a high colour rendering index (CRI = 89.7), and a low colour coordinate temperature (CCT = 4508 K). These results indicate that this highly efficient red-emitting phosphor has great potential as a red component for pc-WLEDs, opening a new perspective for developing new phosphor materials.

K2Ln(PO4)(WO4):Tb3+,Eu3+ (Ln = Y, Gd and Lu) phosphors: highly efficient pure red and tuneable emission for white light-emitting diodes

2015 ◽  
Vol 3 (9) ◽  
pp. 2107-2114 ◽  
Author(s):  
Dawei Wen ◽  
Jiajun Feng ◽  
Junhao Li ◽  
Jianxin Shi ◽  
Mingmei Wu ◽  
...  
Keyword(s):  
Quantum Efficiency ◽  
White Light ◽  
Light Emitting Diodes ◽  
Internal Quantum Efficiency ◽  
Red Phosphor ◽  
Light Emitting ◽  
Highly Efficient ◽  
White Light Emitting Diodes

K2Tb0.5Eu0.5(PO4)(WO4) red phosphor with an internal quantum efficiency of 76.45% is produced. Furthermore, the luminescence colour can be tuned from green to red by adjusting the ratio of Tb3+ and Eu3+.

scholarly journals Strengthening Thermal Stability in V2O5-ZnO-BaO-B2O3-M(PO3)n Glass System (M = Al, Mg) for Laser Sealing Applications

2021 ◽  
Vol 11 (10) ◽  
pp. 4603
Author(s):  
Soyoung Kim ◽  
Karam Han ◽  
Seonhoon Kim ◽  
Linganna Kadathala ◽  
Jinhyeok Kim ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Thermal Expansion ◽  
Bond Strength ◽  
Coefficient Of Thermal Expansion ◽  
Glass Frit ◽  
Glass System ◽  
Fiber Types ◽  
Hermetic Sealing ◽  
Doped Glasses ◽  
Glass Panels

Today, the most common way of laser sealing is using a glass frit paste and screen printer. Laser sealing using glass frit paste has some problems, such as pores, nonuniform height, imperfect hermetic sealing, etc. In order to overcome these problems, sealing using fiber types of sealant is attractive for packaging devices. In this work, (70-x)V2O5-5ZnO-22BaO-3B2O3-xM(PO3)n glasses (mol%) incorporated with xM(PO3)n concentration (where M = Mg, Al, n = 2, 3, respectively) were fabricated and their thermal, thermomechanical, and structural properties were investigated. Most importantly, for this type of sealing, the glass should have a thermal stability (ΔT) of ≥80 °C and the coefficient of thermal expansion (CTE) between the glass and panel should be 1.0 ppm/°C. The highest thermal stability ΔT of the order of 93.2 °C and 112.9 °C was obtained for the 15 mol% of Mg(PO3)2 and Al(PO3)3 doped glasses, respectively. This reveals that the bond strength and connectivity is more strongly improved by trivalent Al(PO3)3. The CTE of a (70-x)V2O5-5ZnO-22BaO-3B2O3-xAl(PO3)3 glass system (mol%) (where x = 5–15, mol%) is in the range of 9.5–15.5 (×10−6/K), which is comparable with the CTE (9–10 (×10−6/K)) of commercial DSSC glass panels. Based on the results, the studied glass systems are considered to be suitable for laser sealing using fiber types of sealant.

Enhanced Negative Thermal Expansion Property Deduced by the Breaks of Superstructure

2021 ◽  
Vol 13 (4) ◽  
pp. 556-562
Author(s):  
Niu Zhang ◽  
Ming-Yi Wu ◽  
Ya-Ming Liu ◽  
Meng-Jie Yang ◽  
Ming-Ju Chao ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Thermal Expansion ◽  
Wide Temperature Range ◽  
Potential Application ◽  
Negative Thermal Expansion ◽  
Thermal Expansion Property ◽  
Expansion Property ◽  
Good Potential ◽  
Nested Structure

The HfV2O7/HfMo2O8 composite were prepared in situ. The phase, structure and thermal expansion property were analyzed. The results indicate the composite consist of cubic HfV2O7 and hexagonal HfMo2O8. The two types of structures were coexisted and mixed uniformly, and interacted with each other. The mutual nested structure suppressed the formation of 3×3×3 superstructure in HfV2O7 (RT) introduced by the reaction in situ. The promoted coupled rotation of quasi-rigid polyhedron units could enhance the negative thermal expansion (NTE) property. The HfV2O7/HfMo2O8 composite exhibits excellent NTE property from 250 to 673 K (at least) with CTE -3.09 × 10-6 K-1. The good NTE property and thermal stability over a wide temperature range, especially near the RT range, bring a good potential application in designing zero thermal expansion materials.

A novel material of HfScMo2VO12 with negative thermal expansion and intense white-light emission

RSC Advances ◽  
2016 ◽  
Vol 6 (59) ◽  
pp. 53657-53661 ◽  
Author(s):  
Yongguang Cheng ◽  
Yuan Liang ◽  
Xianghong Ge ◽  
Xiansheng Liu ◽  
Baohe Yuan ◽  
...  
Keyword(s):  
Thermal Expansion ◽  
White Light ◽  
Light Emission ◽  
Negative Thermal Expansion ◽  
White Light Emission ◽  
Novel Material

A novel material of HfScMo2VO12 with negative thermal expansion (NTE) and intense white-light emission is presented.

A green synthetic route to the highly efficient K2SiF6:Mn4+narrow-band red phosphor for warm white light-emitting diodes

2018 ◽  
Vol 6 (11) ◽  
pp. 2741-2746 ◽  
Author(s):  
Ziyang Hou ◽  
Xueyuan Tang ◽  
Xuefang Luo ◽  
Tianliang Zhou ◽  
Lin Zhang ◽  
...  
Keyword(s):  
White Light ◽  
Light Emitting Diodes ◽  
Narrow Band ◽  
Synthetic Route ◽  
Red Phosphor ◽  
Light Emitting ◽  
Highly Efficient ◽  
Warm White Light ◽  
White Light Emitting Diodes

A green synthetic route to the highly efficient K2SiF6:Mn4+narrow-band red phosphor for warm white light-emitting diodes.

Synthesis and properties of low coefficient of thermal expansion copolyimides derived from biphenyltetracarboxylic dianhydride with p-phenylenediamine and 4,4′-oxydialinine

e-Polymers ◽  
2016 ◽  
Vol 16 (4) ◽  
pp. 295-302 ◽  
Author(s):  
Yonglin Lei ◽  
Yuanjie Shu ◽  
Jinhua Peng ◽  
Yongjian Tang ◽  
Jichuan Huo
Keyword(s):  
Thermal Stability ◽  
Thermal Expansion ◽  
Coefficient Of Thermal Expansion ◽  
Thermomechanical Analysis ◽  
Amic Acid ◽  
Molar Ratio ◽  
Structure And Property ◽  
Property Relations ◽  
Ft Ir ◽  
Biphenyltetracarboxylic Dianhydride

AbstractA series of copolyimides were prepared by thermal imidization of poly(amic acid)s (PAAs) derived from 3,3′,4,4′-biphenyltetracarboxylic dianhydride (s-BPDA), 2,3′,3,4′-biphenyltetracarboxylic dianhydride (a-BPDA), p-phenylenediamine (PDA) and 4,4′-oxydialinine (4,4′-ODA) commonly used for the production of commercial polyimides. The flexible copolyimide films were obtained from that the molar ratio of s-BPDA, a-BPDA, PDA and 4,4′-ODA was 9:1:8:2 (Co-PIs-3), 8:2:9:1 (Co-PIs-5) and 8:2:8:2 (Co-PIs-6). These obtained copolyimide films were characterized by Fourier transform-infrared spectroscopy(FT-IR), wide angle X-ray (WAXD), Thermogravimetric (TG), dynamic mechanical thermal analysis (DMA), thermomechanical analysis (TMA), field-emission scanning electron microscopy (FE-SEM) and mechanical properties measurement. The results showed that three copolyimides remained semi-crystalline and exhibited high glass transition temperature (Tg), high thermal stability, great ultimate tensile strength and low coefficient of thermal expansion (CTE). The Co-PIs-5 had lower crystallinity, lower CTE, greater elongation at break, higher Tg and thermal stability and the greater dense extent, compared with Co-PIs-3 and Co-PIs-6. Structure and property relations of the prepared polyimides were also briefly discussed. The results revealed that the copolymerization of s-BPDA/PDA with a small number of 4,4′-ODA/a-BPDA was a useful means for enhancing flexibility without sacrificing low CTE.

scholarly journals A Proposal for a Composite with Temperature-Independent Thermophysical Properties: HfV2–HfV2O7

Materials ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 5021
Author(s):  
Philipp Keuter ◽  
Anna L. Ravensburg ◽  
Marcus Hans ◽  
Soheil Karimi Aghda ◽  
Damian M. Holzapfel ◽  
...  
Keyword(s):  
Thermal Expansion ◽  
Temperature Coefficient ◽  
Thermophysical Properties ◽  
Coefficient Of Thermal Expansion ◽  
Negative Thermal Expansion ◽  
Phase Fraction ◽  
Formation Temperature ◽  
Oxygen Mobility ◽  
Zero Temperature ◽  
Coefficient Of Elasticity

The HfV2–HfV2O7 composite is proposed as a material with potentially temperature-independent thermophysical properties due to the combination of anomalously increasing thermoelastic constants of HfV2 with the negative thermal expansion of HfV2O7. Based on literature data, the coexistence of both a near-zero temperature coefficient of elasticity and a coefficient of thermal expansion is suggested for a composite with a phase fraction of approximately 30 vol.% HfV2 and 70 vol.% HfV2O7. To produce HfV2–HfV2O7 composites, two synthesis pathways were investigated: (1) annealing of sputtered HfV2 films in air to form HfV2O7 oxide on the surface and (2) sputtering of HfV2O7/HfV2 bilayers. The high oxygen mobility in HfV2 is suggested to inhibit the formation of crystalline HfV2–HfV2O7 composites by annealing HfV2 in air due to oxygen-incorporation-induced amorphization of HfV2. Reducing the formation temperature of crystalline HfV2O7 from 550 °C, as obtained upon annealing, to 300 °C using reactive sputtering enables the synthesis of crystalline bilayered HfV2–HfV2O7.

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