NaGdS2 Phosphor Production via Segmented Sulfurization
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Solution Overview
Problem
Existing methods for producing NaGdS2-based phosphors face challenges in achieving high emission intensity due to impurity mixtures and difficulties in controlling residual oxygen, especially during large-scale production, which affects grain growth and emission intensity.
Innovation Solution
A method involving a raw material mixture of oxide or halide compounds of sodium, rare earth elements, and activating elements, burned in a boron nitride vessel at 1000°C or lower, followed by a second burning step in a quartz glass vessel at 900°C or higher, to regulate oxygen content and enhance crystal growth and emission intensity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If oxide-based raw materials are used and sulfurized by burning in hydrogen sulfide, then the phosphor can be produced with relatively high purity and easily available materials, but a relatively large amount of residual oxygen remains and grain growth is insufficient, reducing emission intensity
Solution Approach 1:
The production process is divided into two distinct burning steps: a first burning step at lower temperature (900-1000°C) to form the basic phosphor structure, and a second burning step at higher temperature (1000-1100°C) to remove residual oxygen and enhance grain growth. This segmentation allows each step to optimize for specific objectives, resolving the contradiction between maintaining purity and achieving high emission intensity.
Solution Approach 2:
The invention changes the temperature parameter between the two burning steps to achieve different objectives. The first step uses moderate temperature to form the phosphor matrix with controlled oxygen content, while the second step uses high temperature to specifically target residual oxygen removal and grain growth enhancement, thereby improving emission intensity without compromising the purity established in the first step.
2Ease of manufacture
If sulfide-based raw materials are used, then the production process is simple and oxygen mixture is minimal, but high-purity sulfide materials are not easily available and impurity mixture makes it difficult to improve emission intensity
Solution Approach 1:
The invention uses oxide-based raw materials as intermediaries that are easily available and can be processed into high-purity phosphor through controlled burning in hydrogen sulfide atmosphere. The oxide materials serve as a mediator between the simple production process and the requirement for high emission intensity, as they can be purified and transformed into the desired phosphor form with controlled composition.
Solution Approach 2:
By changing the chemical form of raw materials from sulfides to oxides, and controlling the burning temperature and atmosphere parameters, the invention achieves both ease of manufacture and high emission intensity. The oxide-based approach with controlled sulfurization allows for better purity and emission characteristics compared to direct sulfide processing.
3Device complexity
If residual oxygen is not controlled, then the production process is simpler, but grain growth is insufficient and emission intensity is reduced
Solution Approach 1:
The production process is segmented into two burning steps with different temperature conditions. The first step establishes the basic phosphor structure, while the second step specifically targets residual oxygen removal and grain growth enhancement. This segmentation adds minimal complexity while significantly improving emission intensity through controlled oxygen management.
Solution Approach 2:
The invention maintains continuous burning in hydrogen sulfide atmosphere throughout both steps, ensuring consistent chemical environment. The second burning step continues the sulfurization process initiated in the first step while adding the specific function of residual oxygen removal and grain growth promotion, thereby maintaining useful action continuity while achieving multiple objectives.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively reduces residual oxygen and promotes crystal growth, resulting in phosphors with improved emission intensity and luminance, suitable for both small-scale and large-scale production.
Implementation Method 1
burning the raw material mixture, which is filled in a boron nitride vessel, in a hydrogen sulfide atmosphere
Implementation Method 2
burning the first burned product, which is filled in a quartz glass vessel, in a hydrogen sulfide atmosphere at a temperature that is equal to or higher than 900° C. and is higher than the burning temperature of the first burning
Implementation Method 3
promotes crystal growth, resulting in phosphors with improved emission intensity
Data Source
AI summary
A phosphor of an embodiment has a composition represented by a composition formula: NaxRMySzOa, where R represents at least one element selected from the group consisting of Y, La, Gd, and Lu, M represents at least one element selected from the group consisting of Bi, Ce, Eu, and Pr, x is an atomic ratio satisfying 0.93<x<1.07, y is an atomic ratio satisfying 0.00002<y<0.01, z is an atomic ratio satisfying 1.9<z<2.1, and a is an atomic ratio satisfying 0.001<a<0.05.