Ba-Doped CaS:Eu Red Phosphor Moisture Resistance
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Solution Overview
Problem
CaS:Eu series red phosphors are prone to hydrolysis when exposed to moisture, leading to emission intensity reduction and hydrogen sulfide gas generation, which can corrode metal components in white LED elements, causing reflective performance and electrical defects.
Innovation Solution
A red phosphor with Ba doping at 0.001 to 1.00 mol% in CaS or (Ca1-xSr)xS, where Ba is not substituted into the crystal lattice, and a metal oxide layer on the phosphor surface to absorb hydrogen sulfide gas, enhancing moisture resistance and suppressing corrosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If CaS:Eu series red phosphor is used to achieve deep red color and narrow peak width, then color purity is improved, but moisture resistance deteriorates due to hydrolysis reaction
Solution Approach 1:
A fluoride coating layer is applied to the surface of the CaS:Eu phosphor particles as an intermediary protective barrier. This fluoride layer prevents direct contact between moisture and the phosphor surface, blocking the hydrolysis reaction while allowing the underlying phosphor to maintain its deep red color emission properties.
Solution Approach 2:
The invention creates a composite structure consisting of the CaS:Eu phosphor core combined with a fluoride coating shell. This composite material approach allows the interior phosphor to provide excellent color purity while the exterior fluoride layer provides moisture resistance, resolving the contradiction between color performance and environmental stability.
2Illumination intensity
If CaS:Eu phosphor is used to achieve deep red color, then emission intensity is improved, but hydrogen sulfide gas generation increases causing corrosion of metal components
Solution Approach 1:
The fluoride coating layer serves as a protective intermediary that prevents hydrogen sulfide gas generated from the phosphor interior from reaching and corroding metal components such as the Ag reflective film. The coating acts as a barrier that allows the phosphor to maintain high emission intensity while blocking the harmful gas effects.
Solution Approach 2:
The invention acknowledges that hydrogen sulfide gas generation is an inherent property of the CaS:Eu phosphor system, but instead of trying to eliminate it completely, the fluoride coating contains and manages this harmful byproduct, converting it from a corrosive threat into a controlled phenomenon that does not compromise the overall device performance.
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 Ba-doped red phosphor exhibits improved moisture resistance and reduced hydrogen sulfide gas effects, making it suitable for use in white LED light sources and other display technologies without compromising emission efficiency or color purity.
Implementation Method 1
a metal oxide layer containing a metal oxide, present on the red phosphor particle surface
Data Source
AI summary
In order to provide a novel CaS:Eu series red phosphor in which moisture-resistance has been improved, a red phosphor is proposed, containing Ba at 0.001 to 1.00 mol% with respect to CaS in a red phosphor represented by the general formula: CaS:Eu.