Pyrochlore Light-Emitting Ceramic Bi Ta Nb Photodegradation
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Solution Overview
Problem
Conventional light-emitting ceramics, particularly those of the pyrochlore type, suffer from photodegradation when exposed to high energy density light, especially of short wavelengths, leading to a decrease in emission intensity over time, which is undesirable in illumination applications requiring constant emission.
Innovation Solution
A light-emitting ceramic with a pyrochlore type compound containing 0.01 mol % or more of Bi, where M1 is La, Y, Gd, or Lu, M2 is Zr, Sn, or Hf, and M3 is Ta, Nb, or Sb, with specific stoichiometric ratios that minimize photodegradation and deliquescence, is developed. This ceramic is manufactured by firing and heat-treating in a reducing atmosphere, enhancing its resistance to photodegradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional pyrochlore type light-emitting ceramic is used, then high emission quantum yield is achieved, but photodegradation occurs when exposed to high energy density light
Solution Approach 1:
The patent changes the chemical composition parameters of the pyrochlore ceramic by incorporating specific amounts of Bi (0.01-5 mol%), Ta (0.01-5 mol%), and Nb (0.01-5 mol%) elements. This compositional modification alters the material's electronic structure and optical properties, enabling high emission quantum yield while simultaneously improving resistance to photodegradation under high energy density light exposure.
Solution Approach 2:
The patent creates a composite pyrochlore ceramic material by combining multiple elements (M1, M2, M3, Bi, Ta, Nb) in a specific structure. The base pyrochlore compound is enhanced with Bi for emission properties, while Ta and Nb provide structural stability and photodegradation resistance, achieving a synergistic effect that resolves the contradiction between high emission yield and durability.
2Illumination intensity
If light-emitting ceramic is exposed to short wavelength high energy density light, then illumination intensity is maintained, but emission amount gradually decreases due to photodegradation
Solution Approach 1:
The patent incorporates Bi, Ta, and Nb elements in advance during the ceramic synthesis process to preemptively protect against photodegradation. These elements form a stable crystal structure that cushions against the damaging effects of high energy density light, preventing emission degradation before it occurs during service.
Solution Approach 2:
By modifying the stoichiometric ratios and elemental composition of the pyrochlore ceramic, the patent optimizes the material's band structure and defect states. This parameter change enables the ceramic to maintain high emission intensity under short wavelength illumination while extending its operational lifetime by reducing photo-induced degradation mechanisms.
3Use of energy by moving object
If Bi content is increased to improve emission properties, then emission quantum yield increases, but deliquescence occurs
Solution Approach 1:
The patent optimizes the Bi content parameter within a specific range (0.01-5 mol%) and balances it with Ta and Nb concentrations. This parameter optimization achieves the desired emission quantum yield while maintaining compositional stability and preventing deliquescence by avoiding excessive Bi content that would compromise structural integrity.
Solution Approach 2:
The patent creates a multi-element composite pyrochlore ceramic where Bi, Ta, and Nb work synergistically. The Bi provides emission enhancement while Ta and Nb contribute to structural stability and moisture resistance, preventing deliquescence even at optimized Bi concentrations through the stabilizing effect of the composite structure.
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 modified ceramic exhibits reduced photodegradation and maintains high emission quantum yield and translucency, making it suitable for wavelength conversion devices and illumination applications.
Implementation Method 1
a light-emitting ceramic which absorbs at least part of energy of light when irradiated with light such as ultraviolet rays and emits the absorbed energy as light of a wavelength different from the wavelength of the irradiated light
Implementation Method 2
A light-emitting ceramic with a pyrochlore type compound containing 0.01 mol % or more of Bi... is manufactured by firing and heat-treating in a reducing atmosphere, enhancing its resistance to photodegradation
Data Source
AI summary
A light-emitting ceramic that includes a pyrochlore type compound that contains 0.01 mol % or more of Bi with respect to 100 mol % of the general formula M1XM2YM3ZOW, wherein M1 is at least one of La, Y, Gd, Yb, and Lu, M2 is at least one of Zr, Sn, and Hf, M3 is at least one of Ta, Nb, and Sb, X, Y, Z, and W are positive numbers that maintain electrical neutrality, X+Y+Z=2.0, 0.005≤Z≤0.2, and 3X+4Y+5Z is 7.02 or less.