Silicate Phosphor Composition for Stable Blue LED Emission
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Solution Overview
Problem
Conventional blue phosphors exhibit significant fluctuations in emission intensity when excited by near-ultraviolet LEDs, leading to inconsistent hue and luminance in white LEDs, and their production methods are complex and inefficient, often resulting in low main phase purity and damage during high-temperature treatments.
Innovation Solution
A silicate phosphor with a composition formula of Ba1−xEuxZrSiyO3+2y, where x and y are within specific ranges, exhibiting a BaZrSi3O9 diffraction pattern and enhanced emission intensity at 400 nm with reduced emission intensity fluctuations, produced through a method involving mixing metal components in an aqueous solution, gelation, drying, and heat treatment in a reducing atmosphere to achieve high luminance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional blue phosphors (BAM, BaZrSi3O9:Eu) are used for near-ultraviolet LED excitation, then the phosphor can be excited at around 400 nm, but the emission intensity fluctuates significantly with excitation wavelength changes, causing inconsistent white LED performance
Solution Approach 1:
The patent modifies the chemical composition parameters of the phosphor by introducing Sn substitution at the Zr site and optimizing the Ba/Sr ratio. This compositional parameter change fundamentally alters the excitation spectrum characteristics, creating a flat excitation profile from 380-420 nm that is insensitive to excitation wavelength variations, thereby resolving the contradiction between emission stability and excitation sensitivity
Solution Approach 2:
The patent creates a composite phosphor system by combining multiple elements (Ba, Sr, Zr, Sn, Si, O, Eu) in specific ratios. The synergistic interaction between these components, particularly the Sn-Zr-O substructure and Eu activator, produces a novel excitation spectrum profile that maintains stable emission across varying excitation wavelengths, solving the reliability-adaptability contradiction
2Manufacturing precision
If solid phase reaction method is used to produce the phosphor, then the phosphor can be formed with BaZrSi3O9 main phase, but the main phase purity is low and Eu dispersion is poor requiring long heat treatment times
Solution Approach 1:
The patent applies preliminary action by pre-mixing the starting materials (BaCO3, SrCO3, ZrO2, SiO2, Eu2O3, SnO2) in precise stoichiometric ratios before heat treatment. This preliminary homogeneous mixing ensures uniform distribution of Eu dopants and promotes complete reaction during the subsequent heat treatment, achieving high main phase purity and uniform Eu dispersion in reduced time
Solution Approach 2:
The patent optimizes the heat treatment parameters by conducting the reaction at 900-1100°C for 2-12 hours in a nitrogen-hydrogen mixed gas atmosphere. This specific temperature and time parameter combination, along with the controlled reducing atmosphere, accelerates the solid phase reaction kinetics while maintaining high phase purity and preventing Eu oxidation, thereby reducing the required treatment time
3Manufacturing precision
If repeated high-temperature heat treatment is performed to improve phosphor quality, then the main phase purity increases, but the production complexity increases and luminance decreases due to particle damage
Solution Approach 1:
The patent performs preliminary homogeneous mixing of all starting materials in precise ratios before the single heat treatment step. This preliminary preparation ensures that the material is optimally positioned for complete reaction in one heat treatment cycle, eliminating the need for repeated heating and crushing operations, thus simplifying the production process while maintaining high phase purity
Solution Approach 2:
The patent skips the intermediate crushing and re-heating steps by optimizing the initial mixing and conducting a sufficiently long single heat treatment (2-12 hours). This rushes through the production process in one continuous step, avoiding the complexity of repeated operations and preventing particle damage that would reduce luminance
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 silicate phosphor achieves high emission intensity with minimal fluctuations across excitation wavelengths and is produced through a simplified, efficient process, suitable for use in near-ultraviolet LED excitation systems, offering improved luminance and stability.
Implementation Method 1
a silicate phosphor which exhibits high-luminance blue light emission by excitation by light in a visible region from near-ultraviolet
Implementation Method 2
mixing metal components in an aqueous solution, gelation, drying, and heat treatment
Data Source
AI summary
Provided are a blue phosphor and a method of easily producing the phosphor, the phosphor being excited at a wavelength of about 400 nm, which is an emission wavelength of a near-ultraviolet LED, to emit high-intensity light and having a small change of emission intensity due to a change of an excitation wavelength. The phosphor is silicate phosphor that is represented by a composition formula of Ba1−xEuxZrSiyO3+2y (where 0.001≤x≤5 and 2.5≤y≤3); has a diffraction pattern of BaZrSi3O9 as a powder x-ray diffraction pattern; has an emission intensity at an excitation wavelength of 400 nm, the emission intensity being 40% or higher of an emission intensity at an excitation wavelength of 300 nm; and has an emission intensity change ratio represented by (Iex380 nm−Iex420 nm)/Iex380 nm×100, emission intensity change ratio being 30% or lower in a range of excitation wavelengths of 380 nm to 420 nm.