Trivalent rare-earth-ion-activated molybdate based phosphors have attracted great attention for solid-state lighting applications by virtue of their long lifetimes, and efficient luminescence property. The rare-earth ions are represented by a partly filled 4f shell that is completely shielded by 5s2 and 5p6 orbitals. Therefore, emission transitions provide sharp intense lines in the optical spectra [1, 2].
The use of rare-earth element-based phosphor, based on ‘‘line-type’’ f–f transitions, can narrow the emissions to the visible range, resulting in high efficiency and a high-lumen equivalence. In recent years, a flourishing care is concentrated on Li3Ba2Gd3-x(MoO4)8 host matrix for luminescent ions in the interest of their excellent chemical and thermal stability and favourable luminescence characteristics compared to the sulfide- and nitride-based materials.
Moreover, these are environmentally friendly as no toxic gases like sulphide are given out. Li3Ba2Gd3-x(MoO4)8 occur in monoclinic crystal system with space group C2/c in a disordered structure [3].
For this research paper, a series of Li3Ba2Gd3–xPrx (MoO4)8 (x = 0.01, 0.03, 0.05, 0.07and 0.09 mol) and Li3Ba2Gd3–xSmx (MoO4)8 (x = 0.02, 0.04, 0.06, 0.08 and 0.10 mol) red phosphors were synthesized by conventional solid state reaction method.
Table of Contents
1. Introduction
2. Experimental Method
2.1 Preparation of Phosphors
2.2 Characterization
3. Results and discussion
3.1 XRD and size distribution characterization
3.2 FTIR analysis
3.3 Photoluminescence Properties of Li3Ba2Gd3 (MoO4)8: Pr3+:
3.3.1 The excitation and emission spectra of Li3Ba2Gd3 (MoO4)8: Pr3+ phosphor
3.3.2 The excitation and emission spectra of Li3Ba2Gd3 (MoO4)8: Sm3+ phosphor
4. Conclusion:
Research Objectives and Topics
The primary objective of this research is to synthesize and investigate the structural, morphological, and photoluminescence characteristics of Pr3+- and Sm3+-doped Li3Ba2Gd3(MoO4)8 phosphors for potential application as red-emitting components in White LEDs.
- Mechanochemically assisted solid-state synthesis of rare-earth-doped molybdate phosphors.
- Structural and morphological analysis using XRD, SEM, and particle size distribution.
- Investigation of photoluminescence excitation and emission properties for display technologies.
- Comparative analysis of the synthesized phosphors with commercial red-emitting Y2O2S:Eu3+ materials.
- Optimization of dopant concentration to achieve enhanced luminescence intensity.
Excerpt from the Book
1. Introduction
Currently, trivalent rare-earth-ion-activated molybdate based phosphors have fascinated great attention for solid-state lighting applications by virtue of their long lifetimes, and efficient luminescence property. The rare-earth ions are represented by a partly filled 4f shell that is completely shielded by 5s2 and 5p6 orbitals. Therefore, emission transitions provide sharp intense lines in the optical spectra [1, 2]. The use of rare-earth element-based phosphor, based on ‘‘line-type’’ f–f transitions, can narrow the emissions to the visible range, resulting in high efficiency and a high-lumen equivalence. In the recent years, a flourishing care is concentrated on Li3Ba2Gd3-x(MoO4)8 host matrix for luminescent ions in the interest of their excellent chemical and thermal stability and favourable luminescence characteristics compared to the sulfide- and nitride-based materials. Moreover, these are environmentally friendly as no toxic gases like sulphide are given out. Li3Ba2Gd3-x(MoO4)8 occur in monoclinic crystal system with space group C2/c in a disordered structure [3].
They are remarkable host matrices for luminescent ions due to their unique structure, good chemical stability, low temperature preparation, superior luminescence features and low cost raw materials. They have also brought a lot of significance for their unique characteristics like ferroelectricity, laser hosts, phosphors and catalysis [4, 5]. The investigations on the luminescence properties of rare earth doped Li3Ba2Gd3-x(MoO4)8 are scanty. Among these, most of the earlier studies carried on these materials in the past few years specifically focused luminescence properties of the single crystals of Li3Ba2Gd3 (MoO4)8 and Li3Ba2Gd3 (MoO4)8 activated with various lanthanide ions [6]. Recently Song et al [7] studied the crystal structure and optical properties of Li3Ba2Gd3 (MoO4)8:Tm3+. The synthesis and characterisation of single and pure phase Li3Ba2Gd3 (MoO4)8: Eu3+ powders were analysed by Chang et al [8]. Though Eu and Tm doped Li3Ba2Gd3 (MoO4)8 phosphors have been reported earlier, Pr3+ and Sm3+ activated Li3Ba2Gd3 (MoO4)8 materials are not investigated so far.
Summary of Chapters
1. Introduction: Presents the background of rare-earth-activated molybdate phosphors and outlines the motivation for developing new red-emitting materials for solid-state lighting.
2. Experimental Method: Describes the specific solid-state reaction procedures and the characterization techniques utilized to analyze the synthesized phosphor samples.
3. Results and discussion: Details the findings regarding the structural properties, particle size, and specific photoluminescence behaviors of the Pr3+- and Sm3+-doped samples.
4. Conclusion:: Summarizes the key findings, confirming that the optimized phosphor compositions are viable candidates for WLED applications.
Keywords
Red phosphors, W-LED, Molybdate, Mechanochemical synthesis, Photoluminescence, Rare-earth ions, Pr3+, Sm3+, Solid-state lighting, Li3Ba2Gd3(MoO4)8, Crystal structure, Emission spectra, Excitation, Nanophosphors, CIE chromaticity.
Frequently Asked Questions
What is the primary focus of this research?
The work focuses on the synthesis and characterization of Pr3+- and Sm3+-doped Li3Ba2Gd3(MoO4)8 red phosphors to evaluate their suitability for WLED applications.
What are the central themes of this study?
The core themes include material synthesis via solid-state reaction, structural analysis, and the investigation of optical luminescence properties for lighting applications.
What is the main research objective?
The objective is to produce highly luminescent, pure-phase red-emitting nanopowders that can efficiently convert blue/near-UV light from GaN chips into red light.
Which scientific methods were employed in this work?
The researchers used a mechanochemically assisted high-temperature solid-state reaction method, complemented by XRD, SEM, FTIR, and photoluminescence spectroscopy for material characterization.
What topics are discussed in the main body of the text?
The text covers the experimental setup, the structural analysis via XRD and FTIR, and a detailed performance evaluation of the excitation and emission spectra for both Pr3+ and Sm3+ dopants.
Which keywords best characterize this work?
Key terms include red phosphors, W-LED, Molybdate, mechanochemical synthesis, and photoluminescence properties of rare-earth ions.
How does the performance of the developed phosphors compare to commercial alternatives?
The study demonstrates that the red emission intensities of the developed Li3Ba2Gd3(MoO4)8:Pr3+/Sm3+ phosphors are comparable to the commercial Y2O2S:Eu3+ red phosphor.
Why are the Pr3+ and Sm3+ dopants chosen for this host matrix?
These ions were selected to provide full-color luminescence; Pr3+ offers distinct red, green, and blue emissions, while Sm3+ provides a strong orange-red fluorescence useful for WLEDs.
What is the role of the C2/c space group mentioned in the introduction?
It characterizes the monoclinic crystal system of the Li3Ba2Gd3(MoO4)8 host, which is noted for its stability and suitability as a matrix for luminescent ions.
What are the optimal doping concentrations found in the study?
The study determined that the optimal concentration for Pr3+ is 7 mol% and for Sm3+ is 8 mol% to achieve maximum emission intensity.
- Citar trabajo
- John Peter (Autor), 2015, Red phosphors for W-LED applications, Múnich, GRIN Verlag, https://www.grin.com/document/306326
