Sol-Gel Synthesis of Mn-Doped Fluoride Luminescent Materials
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Solution Overview
Problem
Current methods for producing luminescent materials for white LEDs are hindered by the use of expensive and difficult-to-produce rare earth elements and the handling of toxic fluorinated acids, which pose safety concerns and limit the production of materials with optimized luminescence and high color rendering index.
Innovation Solution
A sol-gel synthesis process for luminescent materials of the form AxByFz:Mn, where fluorine is introduced only during the final heat treatment step, eliminating the need for dissolved fluorine sources and rare earth elements, and using metal reagents like alkoxides in an alcoholic solution to form a fluorinated matrix with enhanced luminescence properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If rare earth elements are used to produce red-emitting phosphors for high CRI white LEDs, then the color rendering index is improved, but the manufacturing cost increases and production difficulty increases
Solution Approach 1:
The patent replaces expensive rare earth elements with manganese-doped fluoride compounds that use abundant, low-cost raw materials. The fluoride matrix (AxByFz) doped with manganese serves as a cost-effective alternative to rare earth-based red phosphors, achieving similar or superior CRI performance without the high material costs and complex supply chain requirements of rare earth elements.
2Manufacturing precision
If hydrofluoric acid is used as a fluorine source in sol-gel synthesis, then fluorinated luminescent materials are obtained, but safety hazards increase due to extreme corrosiveness and toxicity
Solution Approach 1:
The patent replaces toxic hydrofluoric acid with safer, non-corrosive fluorine sources such as ammonium fluoride, tetrafluoroboric acid, or fluorinated organic compounds. These alternative reagents provide the necessary fluorine for forming the AxByFz matrix without the extreme hazards of HF, eliminating the need for specialized safety infrastructure while maintaining precise fluorine content control.
Solution Approach 2:
The patent introduces fluorine through intermediary compounds that deliver fluorine ions or fluoride groups to the sol-gel system in a controlled, safe manner. These intermediary fluorine sources react under mild conditions to incorporate fluorine into the growing oxide or fluoride matrix, avoiding the direct use of hazardous hydrofluoric acid while achieving the desired fluorinated luminescent material.
3Temperature
If conventional ceramisation methods are used for synthesizing luminescent materials, then high temperature processing is achieved, but energy consumption increases and equipment complexity increases
Solution Approach 1:
The patent fundamentally changes the processing temperature parameter by using sol-gel chemistry that enables fluorinated luminescent material synthesis at low temperatures (below 100°C during sol-gel processing, and below 1000°C during final heat treatment). This contrasts with conventional ceramisation requiring temperatures above 1000°C, dramatically reducing energy consumption and allowing the use of simpler, less expensive equipment.
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
This process improves safety and reduces costs by avoiding rare earth elements and toxic fluorinated acids, enabling the production of luminescent materials with optimized fluorine content and high color rendering index, suitable for LEDs, while maintaining ease of handling and storage.
Implementation Method 1
the method comprises hydrolysis type reactions and then condensation type reactions
Implementation Method 2
the method comprises hydrolysis type reactions and then condensation type reactions
Implementation Method 3
the sol-gel type processes allow production of luminescent materials at low temperature
Implementation Method 4
c) crystallisation of the solid precursor obtained in step b), by heat treatment in fluorine atmosphere
Implementation Method 5
luminescent materials, i.e. materials that emit light under the effect of excitation
Implementation Method 6
compounds of the nitrides family doped with europium are the solution of choice for this red component. They are characterised by an intense red emission
Data Source
AI summary
A sol-gel process for synthesizing a luminescent material has a general formulation: AxByFz:Mn. A is an element of group 1, 2, 4, NR4 or a combination of elements belonging to those groups, with R═H or an alkyl chain or a combination of chains. B is an element of group 5, 6, 13, 14 and 0<x≤5, 0<y≤2, 5≤z≤7. The sol-gel process includes a) producing a liquid precursor (2, 3) in an alcohol solution by mixing metal reagents (1) with manganese, the mixture being made at pH<8; b) obtaining a solid precursor (5, 6) from the liquid precursor (2, 3) obtained in step a), by eliminating (4) the solvent; c) crystallizing (7, 70) the solid precursor (5, 6) obtained in step b) by thermal treatment in fluorinated atmosphere; and d) retrieving the fluorescent crystalline powder (8) obtained at an end of step c).