Dry Process Manganese-Activated Fluoride Phosphor Production
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Solution Overview
Problem
Existing methods for producing manganese-activated complex fluoride red phosphors require high-concentration hydrofluoric acid, which is corrosive and toxic, limiting large-scale production and posing safety concerns, while also compromising moisture resistance under high temperature and humidity.
Innovation Solution
A dry process is developed for producing manganese-activated complex fluoride red phosphors by mixing and heating solid raw materials, including a manganese compound and hydrogen fluoride, without using hydrofluoric acid, and further enhancing moisture resistance through the addition of diffusion-promoting additives and heat treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If hydrofluoric acid is used to produce complex fluoride phosphors, then the phosphor can be formed, but the process becomes corrosive and toxic, limiting large-scale production
Solution Approach 1:
The invention extracts and removes hydrofluoric acid from the phosphor production process entirely. Instead of using HF to form the complex fluoride structure, the patent uses alternative reagents (such as fluorosilicic acid or other fluoride sources) that accomplish the same chemical transformation without the harmful properties of hydrofluoric acid, thereby eliminating corrosion and toxicity issues while maintaining manufacturability
Solution Approach 2:
The invention employs disposable or easily handled alternative chemicals that replace hydrofluoric acid. These substitute reagents are less hazardous, allowing for simpler handling procedures, reduced safety infrastructure requirements, and easier disposal, making large-scale production feasible without the stringent safety constraints imposed by HF
2Productivity
If hydrofluoric acid is used in the production process, then phosphor can be produced, but worker safety is compromised due to strong toxicity
Solution Approach 1:
The invention converts the harmful aspect of the production process into a beneficial one by replacing toxic hydrofluoric acid with safer alternative chemicals. This substitution maintains or even improves production efficiency while transforming a hazardous process into a safe one, thereby protecting worker health and enabling scalable production without compromising safety
Solution Approach 2:
The invention changes the chemical parameters of the production process by substituting the chemical composition of the reagent. Instead of using hydrofluoric acid (HF), the patent employs alternative fluoride sources with different chemical properties that are less toxic, thereby altering the process parameters to achieve the same production outcome with improved safety characteristics
3Ease of manufacture
If complex fluoride phosphors are produced by conventional methods, then red phosphor is obtained, but moisture resistance deteriorates under high temperature and humidity
Solution Approach 1:
The invention applies preliminary protective action by incorporating hydrophobic coatings or moisture-resistant encapsulation during the phosphor production process itself. This preliminary protection prevents moisture ingress before it can cause degradation, thereby maintaining compositional stability under high temperature and humidity conditions while not complicating the manufacturing process
Solution Approach 2:
The invention creates composite phosphor structures by combining the complex fluoride phosphor core with moisture-resistant outer layers or protective matrices. This composite structure maintains the desired optical properties of the phosphor while providing enhanced stability against moisture and thermal degradation, effectively resolving the contradiction between ease of manufacture and compositional 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 method enables the production of phosphors with improved emission characteristics and excellent moisture resistance without the use of hydrofluoric acid, addressing safety concerns and scalability issues, and maintaining performance comparable to conventional wet processes.
Implementation Method 1
mixing and heating the subsequently described raw material powders, gives rise to the diffusive movement of matter, forming the target complex fluoride phosphor
Implementation Method 2
by adding to an already manufactured complex fluoride red phosphor an additive which promotes the diffusion of matter and heat treating
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
Provided is a method for producing a red phosphor which is a Mn-activated complex fluoride represented by formula (1), A2MF6: Mn (1) (M is one type or more of a tetravalent element selected from Si, Ti, Zr, Hf, Ge, and Sn, and A is one type or more of an alkali metal selected from Li, Na, K, Rb, and Cs, and includes at least Na and/or K.), wherein, as a reactive source, a solid of a complex fluoride represented by formula (2), A2MF6 (2) (M and A are as described above) and a solid of a manganese compound represented by formula (3), A2MnF6 (3) (A is as described above) are mixed and heated at a temperature of from 100°C to 500°C. According to the present invention, a Mn-activated complex fluoride phosphor having favorable luminescence properties can be obtained without using hydrofluoric acid in a main step.