Alpha-Sialon Phosphor Low Oxygen Content Synthesis
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Solution Overview
Problem
Conventional α-sialon phosphors with high oxygen content have limited light-emitting efficiency and crystallinity, and existing methods for producing them result in particles that are not optimally sized for efficient light emission.
Innovation Solution
The development of α-sialon phosphors with a low oxygen content, specifically using calcium nitride raw materials to control the oxygen content and achieve particles with a high aspect ratio and large diameter, which are then synthesized using a heat treatment process to enhance crystallinity and light-emitting characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If oxide raw materials are used to synthesize α-sialon phosphor, then the synthesis process is straightforward, but oxygen is inevitably ingressed and solid-soluted into the crystal lattice, resulting in limited light-emitting efficiency and lower fluorescent peak wavelength
Solution Approach 1:
The patent changes the chemical composition parameter of raw materials from conventional oxides to nitrides (specifically calcium nitride, silicon nitride, aluminum nitride). This parameter change prevents oxygen ingress during synthesis, eliminating the harmful effect of oxygen solid-solution on light-emitting efficiency while maintaining the α-sialon crystal structure formation
Solution Approach 2:
The patent converts the potential harm of using nitride raw materials (which may have lower process familiarity) into a benefit by achieving superior optical properties. The low oxygen content becomes a beneficial feature that enables high light-emitting efficiency and achieves fluorescent peak wavelengths of 595 nm or more, transforming a synthesis challenge into a performance advantage
2Ease of manufacture
If conventional synthesis methods are used, then the process is well-established, but the resulting particles have suboptimal size and aspect ratio, limiting light-emitting efficiency
Solution Approach 1:
The patent changes the physical parameter of particle morphology by controlling synthesis conditions to achieve high aspect ratio particles. The use of nitride raw materials combined with controlled heat treatment produces elongated crystal structures with aspect ratios significantly higher than conventional methods, optimizing light emission properties
Solution Approach 2:
The patent performs preliminary action by carefully selecting and preparing raw materials with specific properties before synthesis. The use of calcium nitride as a calcium source, combined with controlled mixing and synthesis conditions, pre-determines the formation of particles with optimal size and aspect ratio, achieving manufacturing precision of 5 μm or more with high aspect ratios
3Ease of manufacture
If high oxygen content α-sialon is synthesized, then the crystal structure is easier to form, but the fluorescent peak wavelength is limited to below 595 nm and light-emitting efficiency is reduced
Solution Approach 1:
The patent changes the chemical composition parameter by using nitride raw materials instead of oxides, achieving low oxygen content (0.1-5.0 wt%) in the synthesized α-sialon. This parameter change shifts the fluorescent peak wavelength to 595 nm or more while maintaining stable crystal structure formation, resolving the contradiction between ease of formation and optical performance
Solution Approach 2:
The patent copies the beneficial low oxygen content characteristic from the raw material selection (nitride-based) through the synthesis process, maintaining consistent low oxygen levels in the final product. This copying of the low-oxygen state throughout the process ensures the fluorescent peak wavelength remains at 595 nm or more
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 resulting α-sialon phosphors exhibit superior fluorescent characteristics with a peak wavelength of 595 nm or more, maintaining high light-emitting efficiency even in powder form, and are suitable for use in light-emitting apparatuses like LEDs, offering improved crystallinity and ease of particle size control.
Implementation Method 1
α-sialon phosphor that is excited by ultraviolet rays or blue light to emit orange or red light
Implementation Method 2
The α-sialon can be synthesized, for example, by subjecting, to a heat treatment in a nitrogen atmosphere, mixed powders of silicon nitride, aluminum nitride, and the oxides of the ingressed and solid-soluted elements
Data Source
AI summary
α-sialon phosphor that is α-sialon represented by a general expression: (M)x(Eu)y(Si, Al)12(O, N)16 (where M is one or more types of elements selected from a group consisting of Li, Mg, Ca, and Y as well as lanthanide element (except for La and Ce) and including at least Ca), the α-sialon phosphor being structured so that an oxygen content is 1.2 mass % or less and primary particles constituting the α-sialon have a columnar shape. When the α-sialon phosphor receives ultraviolet rays or visible light having a wavelength from 250 to 500 nm as an excitation source, the α-sialon phosphor shows a fluorescent characteristic having a peak in a wavelength region from 595 to 630 nm.