Ceramic Scintillator Production via Pre-Reduction Pulverization
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Solution Overview
Problem
Existing methods for producing ceramic scintillators for X-ray CT apparatuses result in low-density sintered bodies and poor luminescence intensity due to sulfur dissociation during pulverization, leading to increased costs and reduced sensitivity.
Innovation Solution
Conducting a pulverization step before the reduction step to adjust particle sizes, while maintaining the calcining and reduction processes at specific temperatures, prevents sulfur dissociation, allowing for the production of high-density ceramic scintillators with enhanced luminescence intensity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If rare earth oxysulfide powder is wet-pulverized to adjust particle sizes, then particle size distribution is improved, but sulfur dissociates during pulverization causing lattice defects and poor luminescence intensity
Solution Approach 1:
The patent applies preliminary action by conducting the pulverization step before the reduction step. By pulverizing the rare earth oxysulfate powder before reducing it to rare earth oxysulfide, the patent achieves fine particle size distribution while preventing sulfur dissociation that would occur if pulverization were performed after reduction. This sequence ensures that sulfur remains bonded to the rare earth atoms during the mechanical stress of pulverization, maintaining lattice integrity and luminescence properties.
2Ease of manufacture
If rare earth oxysulfide powder contains large particles, then production cost is reduced, but high-density sintered bodies cannot be obtained without hot pressing or hot-isostatic pressing
Solution Approach 1:
The patent applies preliminary action by pulverizing the rare earth oxysulfate powder before reduction, creating fine particles that can be densely packed. This preliminary size reduction eliminates the need for expensive hot pressing or hot-isostatic pressing operations, as the fine particles naturally achieve high density during conventional sintering, thereby reducing manufacturing costs while maintaining high sintered body density.
Solution Approach 2:
The patent applies parameter changes by controlling the particle size of rare earth oxysulfate powder before reduction. By adjusting the particle size parameters of the precursor material, the patent enables subsequent sintering to produce high-density ceramic scintillators using conventional pressureless sintering methods, avoiding the need for high-cost high-pressure sintering processes.
3Reliability
If scintillators have high luminescence intensity, then sensitivity is improved, but radiation exposure time must be reduced to minimize human exposure
Solution Approach 1:
The patent applies parameter changes by optimizing the composition and microstructure of the ceramic scintillator. By controlling the rare earth element composition, sintering temperature, and particle size distribution, the patent enhances luminescence efficiency, allowing shorter exposure times to achieve the same signal intensity, thereby reducing radiation dose to patients while maintaining diagnostic image quality.
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 approach yields ceramic scintillators with high-density and high-sensitivity responses to radiation, reducing exposure time and improving imaging efficiency in X-ray CT applications.
Implementation Method 1
The produced rare earth oxysulfate is reduced in a protective gas such as nitrogen or argon at 500-1,000°C using hydrogen or a hydrocarbon gas to produce a rare earth oxysulfide
Implementation Method 2
The green body is sintered
Implementation Method 3
ceramic scintillators produced by sintering rare earth oxysulfide powder such as Gd 2 O 2 S, Y 2 O 2 S, Lu 2 O 2 S, etc. comprising Pr, Ce, Eu, Tb, etc. as luminescent elements
Data Source
Figure 1
Figure 2~3
AI summary
A method for producing a ceramic scintillator comprising the steps of mixing a rare earth compound with sulfuric acid and/or sulfate to cause their reaction to obtain a product; calcining the product to obtain calcined powder; reducing the calcined powder to obtain rare earth oxysulfide powder; molding the rare earth oxysulfide powder to obtain a green body; and sintering the green body; a pulverization step being conducted to adjust the particle sizes of the product and/or the calcined powder at least before the reduction step. Translation of the Abstract as published by WIPO This method for producing a ceramic scintillator includes: a mixing step for obtaining a product by mixing and reacting a rare earth compound and sulfuric acid and/or a sulfate; a calcining step for obtaining a calcined powder by calcining the product; a reduction step for obtaining a rare-earth oxysulfide powder by reducing the calcined powder; a molding step for obtaining a molded article by molding the rare-earth oxysulfide powder; and a sintering step for sintering the molded article. Furthermore, the method for producing a ceramic scintillator is characterized by including a pulverization step for adjusting the particle diameter of the product and/or the calcined powder prior to at least the reduction step.