Nitride Ceramic Sintered Body Purification via Molybdenum Calcination
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing light emitting devices using nitride fluorescent materials in ceramic sintered bodies face a decrease in luminous flux due to impurities formed during calcination, which adversely affect light emitting characteristics.
Innovation Solution
A method for producing a ceramic sintered body involves preparing a molded body with a nitride fluorescent material, undergoing primary, secondary, and third calcinations under specific conditions, including contact with molybdenum metal and a container with a higher melting point metal, to eliminate impurities and enhance light emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional calcination is performed on nitride fluorescent material, then sintered body is formed, but impurities are generated causing decrease in luminous flux
Solution Approach 1:
The calcination process is divided into three distinct stages: primary calcination to form the sintered body, secondary calcination in contact with molybdenum to eliminate specific impurities, and third calcination in a metal container to remove remaining impurities. This segmentation allows each stage to target specific impurity removal objectives, achieving high purity without compromising the sintered body structure.
Solution Approach 2:
Molybdenum metal serves as an intermediary substance during secondary calcination. The molybdenum contacts the sintered body and selectively reacts with or absorbs specific impurities formed during primary calcination, thereby purifying the sintered body without affecting the fluorescent material's core structure or performance.
2Object-generated harmful factors
If multiple calcination steps are performed to remove impurities, then luminous flux is improved, but production time and process complexity increase
Solution Approach 1:
The secondary and third calcination steps are merged into a coordinated sequence where molybdenum-based impurity removal and container-based impurity removal work together. By combining these complementary purification mechanisms in series, the process achieves comprehensive impurity elimination more efficiently than separate, repeated calcination cycles would provide.
Solution Approach 2:
Each calcination stage uses different parameters: primary calcination uses standard sintering conditions, secondary calcination uses molybdenum contact at controlled temperatures to target specific impurities, and third calcination uses a metal container environment. These parameter changes optimize each stage for specific purification objectives, reducing total time compared to prolonged single-stage calcination.
3Productivity
If conventional single-step calcination is used, then production is simple, but luminous flux decreases due to impurities
Solution Approach 1:
The secondary calcination step with molybdenum is performed as a preliminary action before final product completion. This preliminary impurity removal prevents degradation of light emitting characteristics in subsequent processing and usage, ensuring high reliability without requiring extensive post-processing.
Solution Approach 2:
The three calcination steps form a continuous purification sequence where each stage builds on the previous one. The sintered body undergoes progressive impurity removal without interruption, maintaining useful action throughout the process. This continuous approach ensures consistent high luminous flux output while keeping production flow efficient.
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 results in a ceramic sintered body with high relative density and luminous flux, maintaining light emission intensity and achieving a desired body color without blackening or dullness.
Implementation Method 1
a member containing a fluorescent material that absorbs a part of light emitted from the light emitting element and converts the wavelength to another one
Implementation Method 2
obtaining a first sintered body by performing primary calcination of the molded body; obtaining a second sintered body by performing secondary calcination of the first sintered body
Data Source
AI summary
A method for producing a ceramic sintered body includes: preparing a molded body containing a nitride fluorescent material having the composition containing Si; N; at least one alkaline earth metal element M1; and a metal element M2 being at least one selected from the group consisting of Eu, Ce, Tb, and Mn, to obtain a composition as described in the disclosure; obtaining a first sintered body by performing primary calcination of the molded body; obtaining a second sintered body by performing secondary calcination of the first sintered body in contact with a solid composed of a molybdenum metal or an alloy containing molybdenum as a main component; and obtaining a third sintered body by performing third calcination of the second sintered body while being placed in a container containing a metal having a melting point higher than that of the molybdenum metal.