SiAlON Red Phosphor Composition for Eu2+ Stability

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Eu doped phosphor materials like SrLiAl3N4:Eu and SrLi2Al2O2:Eu face challenges in enhancing their properties due to the incorporation of Eu in both divalent and trivalent states, with high process gas pressures not effectively improving the stability and performance of SrLi2Al2O2:Eu (SLAO) phosphors.

Innovation Solution

The introduction of silicon into the host lattice of Eu doped phosphors to form SiAlON compositions, which crystallize in the SLAO structure type, reduces the concentration of unwanted Eu3+ and enhances stability and conversion efficiency by altering the defect chemistry.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If high process gas pressure is applied to enhance Eu2+ stability in SLAO phosphors, then quantum efficiency increases, but the unit cell volume decreases and the method is not effective for SLAO type phosphors

Engineering Contradiction:

ImproveEu2+ stabilityVSAvoidunit cell volume

Core Design Contradiction:

ReliabilityVSVolume of stationary object

Solution Approach 1:

The patent changes the chemical composition parameters by introducing Si and O into the host lattice to form SiAlON compositions. This compositional parameter change stabilizes Eu2+ through altered defect chemistry without requiring high gas pressure, thus avoiding unit cell volume reduction while maintaining Eu2+ stability and quantum efficiency.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite phosphor material by incorporating Si and O into the SLAO host lattice to form SiAlON compositions. This composite approach combines the benefits of the original SLAO structure with the stabilizing effects of Si and O, achieving Eu2+ stabilization without the adverse effects of high pressure processing.

Inventive Principle:

Principle #40Composite materials

2Ease of manufacture

If Eu activator is incorporated in trivalent state, then phosphor material can be synthesized, but luminescence performance deteriorates due to unwanted Eu3+ incorporation

Engineering Contradiction:

Improvephosphor synthesisVSAvoidluminescence performance

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent changes the chemical environment parameters by introducing Si and O into the host lattice. This alters the defect chemistry and local coordination environment, creating conditions that favor Eu2+ over Eu3+ incorporation. The modified chemical parameters enable synthesis while suppressing unwanted Eu3+ formation, thus maintaining both manufacturability and luminescence performance.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The introduced Si and O act as intermediaries that modify the chemical environment and defect structure of the host lattice. These intermediary elements mediate between the Eu activator and the host, creating a chemical environment that preferentially stabilizes Eu2+ and reduces Eu3+ incorporation, thereby improving luminescence performance without compromising synthesis ease.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Productivity

If phosphor concentration in optical path is increased to improve light absorption, then conversion efficiency increases, but device complexity increases

Engineering Contradiction:

Improvelight conversion efficiencyVSAvoidphosphor layer structure

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent changes the intrinsic optical parameters of the phosphor material by introducing Si and O to form SiAlON compositions. This enhances the phosphor's quantum efficiency and luminescence properties, allowing for improved light conversion efficiency at lower phosphor concentrations, thereby reducing device complexity while maintaining or improving productivity.

Inventive Principle:

Principle #35Parameter changes

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 novel SiAlON phosphor compositions exhibit improved luminescence properties, increased stability, and enhanced operation lifetime of phosphor-converted LEDs, enabling the production of white light with high color rendering index and red emitting LEDs with minimized long wavelength light intensity distribution.

Implementation Method 1

Methodology Applied

Scientific EffectDefect chemistry:

Implementation Method 2

Eu doped phosphor materials like SrLiAl3N4:Eu and SrLi2Al2O2:Eu

Methodology Applied

Scientific EffectPhotoluminescence: Photoluminescence

Data Source

PatentUS11926775B2Narrow band emitting SiAION phosphor

Publication Date: 2024.03.12 LUMILEDS SINGAPORE PTE LTD

AI summary

This specification discloses methods of enhancing the stability and performance of Eu2+ doped narrow band red emitting phosphors. In one embodiment the resulting phosphor compositions are characterized by crystallizing in ordered structure variants of the UCr4C4 crystal structure type and having a composition of AE1−xLi3−2yAl1+y−zSizO4−4y−zN4y+z:Eux (AE=Ca, Sr, Ba, or a combination thereof, 0<x<0.04, 0≤y<1, 0<z<0.05, y+z≤1). It is believed that the formal substitution (Al,O)+ by (Si,N)+ reduces the concentration of unwanted Eu3+ and thus enhances properties of the phosphor such as stability and conversion efficiency.