Nitride Phosphor Brightness Stability Under Blue LED Excitation
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Solution Overview
Problem
Conventional phosphors experience significant brightness deterioration when exposed to high-energy excitation sources, necessitating the development of phosphors with improved chemical and thermal stability and emission characteristics for applications in LED lighting and display devices.
Innovation Solution
A phosphor with a novel inorganic compound structure represented by A2(D, E)5X9, where A, D, E, and X include elements like Mg, Ca, Sr, Si, Al, and N, and an activating element such as Eu, which exhibits high emission intensity and stability, allowing for the creation of a blue-to-red emission spectrum suitable for white LED applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional phosphors (silicate, phosphate, aluminate, sulfide) are used, then they can provide basic luminescence function, but they experience significant brightness deterioration when exposed to high-energy excitation sources
Solution Approach 1:
The patent changes the chemical composition parameters by incorporating nitrogen into the crystal structure to form nitride and oxynitride compounds. This fundamental compositional change transforms the phosphor's resistance to high-energy excitation, eliminating brightness deterioration while maintaining stable luminescence output under UV and blue light excitation
Solution Approach 2:
The patent creates composite phosphor materials by combining multiple elements (rare earth metals like Eu, Ce, Pr, Nd, Sm, Tb, Dy, Yb with metal compounds) to form complex nitride and oxynitride crystal structures. These composite materials exhibit superior chemical and thermal stability compared to conventional single-phase phosphors, resolving the brightness stability issue
2Reliability
If inorganic crystal with nitrogen (nitride/oxynitride phosphor) is used instead of conventional phosphor, then brightness deterioration is reduced, but manufacturing complexity increases due to high firing temperature requirements
Solution Approach 1:
The patent optimizes the firing temperature parameter to specific ranges (1200-2200°C) and controls the nitrogen atmosphere pressure (0.1-100 MPa) to achieve complete reaction and stable crystal formation. By precisely controlling these parameters, the patent simplifies the manufacturing process while ensuring high brightness stability of the resulting nitride/oxynitride phosphor
3Reliability
If high firing temperature (1200-2200°C) is applied to synthesize nitride/oxynitride phosphor, then chemical and thermal stability is improved, but energy consumption increases
Solution Approach 1:
The patent establishes an optimal firing temperature range (1200-2200°C) that balances energy input with output quality. Within this range, the phosphor achieves maximum chemical and thermal stability with minimal energy waste, as lower temperatures produce incomplete reactions while higher temperatures cause unnecessary energy consumption without proportional improvement in stability
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 phosphor achieves high emission intensity and stability, maintaining brightness even under high-energy excitation, and can be used in various display devices and lighting applications, offering improved durability and color rendering properties.
Implementation Method 1
a phosphor having an inorganic crystal containing nitrogen in a crystal structure thereof as a host crystal... has been proposed, as exemplified by a sialon phosphor, an oxynitride phosphor, or a nitride phosphor, which is characterized by low brightness deterioration caused by high energy excitation
Data Source
AI summary
Provided is chemically and thermally stable phosphor having light-emitting characteristics different from the conventional phosphor and high emission intensity when combined with LED of not exceeding 470 nm. The phosphor comprises inorganic compound having crystal represented by A2(D,E)5X9; crystal represented by Ca2Si5O3N6; or inorganic crystal having the same crystal structure as crystal represented by Ca2Si5O3N6, which includes A, D, E, and X elements (A is one or more kinds selected from Mg, Ca, Sr, and Ba; D is one or more kinds selected from Si, Ge, Sn, Ti, Zr, and Hf; E is one or more kinds selected from B, Al, Ga, In, Sc, Y, and La; and X is one or more kinds selected from O, N, and F), in which M element (M is one or more kinds of elements selected from Mn, Ce, Pr, Nd, Sm, Eu, Tb, Dy, and Yb) is solid-solved.