Nitride-Based Phosphor Synthesis via Segmented Sintering
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Solution Overview
Problem
Conventional methods for synthesizing oxynitride-based phosphors face challenges in achieving single-phase production with high Eu concentration due to excessive oxygen content, leading to impurity formation and reduced emission efficiency, especially at high temperatures.
Innovation Solution
A two-step sintering process is employed, dividing precursors into groups and sintering them at different temperatures under nitrogen and hydrogen gas atmospheres, which allows for the formation of a nitride-based phosphor with a composition formula M1-zEuzSiaObNc, enabling the synthesis of a single-phase phosphor with improved high-temperature stability and emission characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If high-concentration Eu is added to oxynitride-based phosphor synthesis, then emission characteristics improve, but oxygen content becomes excessive and impurities form
Solution Approach 1:
The synthesis process is divided into two sequential sintering steps: first forming the oxynitride base structure with controlled oxygen content, then adding Eu in the second step to avoid oxygen excess and impurity formation while achieving high emission characteristics
Solution Approach 2:
The oxynitride base structure (MSi2O2N2) is pre-formed in the first sintering step before Eu addition, establishing a stable crystalline framework that prevents oxygen excess and impurity formation during subsequent Eu incorporation
2Ease of manufacture
If conventional solid phase method is used for oxynitride synthesis, then manufacturing simplicity is maintained, but single-phase production is difficult when high Eu concentration is added
Solution Approach 1:
The conventional single-step solid phase synthesis is segmented into two sequential sintering steps, where the first step forms the oxynitride base structure and the second step incorporates Eu, enabling single-phase production with high Eu concentration while maintaining manufacturing simplicity
Solution Approach 2:
The synthesis parameters are changed by implementing two distinct sintering temperatures and atmospheric conditions, allowing precise control over phase formation and enabling single-phase production that cannot be achieved with conventional single-step methods
3Illumination intensity
If high Eu concentration is added in single step synthesis, then emission intensity improves, but oxygen content becomes excessive leading to reduced high-temperature stability
Solution Approach 1:
The synthesis is segmented into two steps where Eu is added only in the second sintering step after the oxynitride base structure is formed, preventing oxygen excess and maintaining compositional stability at high temperatures while achieving high emission intensity
Solution Approach 2:
The oxynitride base structure is preliminarily formed with controlled oxygen content before Eu addition, establishing a stable compositional foundation that maintains high-temperature stability while allowing high Eu concentration for intense emission
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
The method results in a nitride-based phosphor with at least 80% emission intensity at high temperatures, comparable to conventional YAG phosphors, while reducing impurity production and enhancing crystallinity, thus offering superior performance in LED applications.
Implementation Method 1
The first sintering step divides a plurality of precursors into at least two groups and sinters the respective groups. The second sintering step mixes and sinters products generated after the sintering of respective ones of the at least two groups.
Implementation Method 2
The second sintering step may be performed under a nitrogen and hydrogen gas atmosphere.
Data Source
AI summary
Disclosed is a method for preparing a fluorescent substance, which is represented by the formula M1-zEuzSiaObNc (M=Sr1-x-yBaxCay, 0 x 0.5, 0 y 0.2, 0<z 0.3, 2 a 2.5, 1.5 b 2, and 2 c 2.5), and the present invention provides the method for preparing a nitride-based fluorescent substance comprising the following steps: a preliminary firing step further comprising a first firing step of creating a first firing product by mixing and firing a first precursor group including an M precursor and a first silicon precursor, and a second firing step of creating a second firing product by mixing and firing a second precursor group including an Eu precursor and a second silicon precursor; and a secondary firing step of mixing and firing the first firing product and the second firing product.