Nitride Phosphor Tuning for LED Thermal Stability
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Solution Overview
Problem
Current nitride phosphors have difficulty in adjusting their emission spectrum, limiting their photochromic property flexibility and thermal stability for high-density energy excitation requirements in advanced LED applications.
Innovation Solution
A phosphor comprising an inorganic compound with specific elements (Lu, La, Si, N, Ce, and Dy) that allows for adjustable emission spectrum and enhanced thermal stability, achieved through a preparation method involving calcination and subsequent processing to optimize crystal structure and ligand site contraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If nitride phosphor is used to improve thermal stability, then thermal stability is improved, but emission spectrum adjustability deteriorates
Solution Approach 1:
The patent applies parameter changes by systematically varying the doping concentration of Ce and Dy ions, as well as the stoichiometric ratios of elements in the M3-aAxDy:aR compound. By adjusting these compositional parameters, the emission spectrum can be tuned across different wavelengths while maintaining the thermal stability provided by the nitride base structure. This resolves the contradiction by showing that spectrum adjustability and thermal stability are not mutually exclusive if the right compositional parameters are selected.
Solution Approach 2:
The patent employs composite materials by combining multiple elements (M=Lu, La, Pr, Nd, Sm, Y, Tb, or Gd; A=Si and/or Ge; D=O, N, and F; R=Ce and/or Dy) into a single phosphor compound with formula M3-aAxDy:aR. This composite structure integrates the thermal stability of nitride compounds with the可调 photochromic properties of rare earth dopants, achieving both high thermal stability and flexible emission spectrum adjustment simultaneously.
2Ease of manufacture
If aluminate-series phosphor is used to achieve mature phosphor system, then market availability is improved, but thermal stability under high-density energy excitation deteriorates
Solution Approach 1:
The patent transitions from aluminate-series to nitride-based phosphor by changing the anionic parameter (from oxide to nitride), which fundamentally improves thermal stability under high-density energy excitation. The chemical composition M3-aAxDy:aR with nitride as the base provides enhanced thermal resistance while maintaining manufacturability through established ceramic processing techniques.
Solution Approach 2:
The patent creates a new composite material system M3-aAxDy:aR that combines rare earth elements with nitride and silicide/germanide components. This composite structure achieves superior thermal stability compared to conventional aluminate phosphors while incorporating Ce and Dy dopants for可调 luminescence properties, making it suitable for high-power LED applications.
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's emission spectrum can be easily adjusted to the green light region, providing flexible photochromic properties and meeting the thermal stability needs for high-density energy excitation, resulting in improved light emission efficiency and stability for LED devices.
Implementation Method 1
The phosphor has a peak wavelength of excitation spectrum at 420 to 460 nm, and can emit a peak wavelength covering the range between 515 to 540 nm
Implementation Method 2
calcinating the same in nitrogen or other non-oxidizing conditions to obtain a calcinated product, wherein the highest sintering temperature is from 1500 to 2000° C.
Implementation Method 3
the original ligand site would be contracted; in order to reduce lattice distortion due to the ligand site contraction, the adjacent ligand site expands, and this weakens the existing crystal field environment
Data Source
AI summary
Phosphor, a preparation method for the phosphor, and a light emitting device having the phosphor. The phosphor comprises an inorganic compound which at least comprises an element M, an element A, an element D, and an element R; the element M is one or two elements selected from the group consisting of Lu, La, Pr, Nd, Sm, Y, Tb, and Gd and must comprise Lu; the element A is Si and/or Ge; the element D is one or two elements selected from the group consisting of O, N, and F and must comprise N; the element R is Ce and/or Dy. Since the ionic radius of Lu3+ is smaller than that of La3+, when the inorganic compound comprises element Lu, the original ligand site would be contracted. In order to reduce lattice distortion due to the ligand site contraction, the adjacent ligand site expands, and the photochromic property is adjusted.