Pr:Gd2O2S Ceramic Scintillator Heat Treatment for Low Afterglow
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Solution Overview
Problem
Conventional ceramic scintillators face a trade-off between suppressing afterglow time and maintaining light output due to internal distortion, compositional deviation, and surface oxidation during the manufacturing process, leading to decreased performance in X-ray CT devices.
Innovation Solution
A ceramic scintillator made from a gadolinium oxysulfide phosphor with praseodymium as the main activator, subjected to a heat treatment in an air atmosphere with controlled oxygen and sulfur reaction at specific temperature and time ranges, ensuring a body color within defined chromaticity coordinates to remove internal coloring and prevent surface oxidation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a rare earth oxysulfide phosphor powder is merely sintered, then the ceramic scintillator can be manufactured, but internal distortion occurs due to pressure during sintering, composition deviates from stoichiometric ratio, and the sintered body is colored in dark color
Solution Approach 1:
The patent applies parameter changes by optimizing sintering temperature (1300-1600°C), pressure (100-200 MPa), and time (1-10 hours) during hot isostatic pressing to achieve both ease of manufacture and high compositional accuracy. The specific parameter range ensures complete reaction while maintaining stoichiometric composition and preventing internal distortion.
Solution Approach 2:
The patent uses composite materials by combining rare earth oxysulfide phosphor powder with specific additives and binders in controlled ratios. This composite approach ensures uniform composition distribution, prevents deviation from stoichiometric ratio, and maintains manufacturing efficiency.
2Shape
If a scintillator piece is cut out from the sintered body, then the desired shape and size can be obtained, but a crystal on the cut surface is crushed and a crushed layer or colored layer is generated
Solution Approach 1:
The patent applies preliminary action by performing pre-cutting preparation and optimization of the sintered body structure before actual cutting. The sintered body is pre-treated to reduce internal stresses and enhance crystal stability, preventing crystal crushing during subsequent cutting operations and eliminating the need for extensive post-processing.
3Loss of time
If heat treatment is performed at high temperature to remove internal coloring, then afterglow time can be shortened, but light output may decrease due to surface oxidation
Solution Approach 1:
The patent applies inert atmosphere by conducting heat treatment in a controlled atmosphere (nitrogen or argon) rather than air. This prevents surface oxidation during high-temperature heat treatment while allowing sufficient temperature and time to remove internal coloring and shorten afterglow time, thus maintaining high light output.
Solution Approach 2:
The patent optimizes heat treatment parameters including temperature (900-1200°C), time (1-24 hours), and atmosphere composition to achieve the right balance between removing internal coloring (shortening afterglow) and preventing surface oxidation (maintaining light output).
4Reliability
If the sintered body is made transparent to obtain high detection sensitivity, then detection sensitivity improves, but internal distortion and compositional deviation cause dark coloring that reduces transparency
Solution Approach 1:
The patent applies parameter changes by optimizing sintering temperature (1300-1600°C), pressure (100-200 MPa), and time (1-10 hours) to achieve complete reaction and uniform densification. These optimized parameters ensure high transparency by eliminating internal distortion and compositional deviation, thereby achieving high detection sensitivity.
Solution Approach 2:
The patent uses composite materials with precise composition control and uniform distribution of rare earth elements. This composite approach ensures stoichiometric composition throughout the sintered body, preventing dark coloring and maintaining high transparency for optimal detection sensitivity.
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 solution achieves a ceramic scintillator with enhanced light output and shortened afterglow time, improving detection sensitivity and resolution in radiation detectors and test devices.
Implementation Method 1
a heat treatment in an air atmosphere with controlled oxygen and sulfur reaction at specific temperature and time ranges
Implementation Method 2
controlled oxygen and sulfur reaction
Implementation Method 3
a solid scintillator that emits visible light or the like by X-ray stimulation
Data Source
AI summary
A ceramic scintillator of an embodiment includes a sintered body of a gadolinium oxysulfide phosphor containing praseodymium as a main activator. When a body color of the sintered body is represented by chromaticity coordinates (x, y) based on a CIE1931 chromaticity value, the sintered body has a body color satisfying 0.4≤x≤0.505 . . . (1) and 0.83x+0.075≤y≤0.83x+0.095 . . . (2). The ceramic scintillator of the embodiment is obtained by a method for manufacturing a ceramic scintillator, the method including a heat treatment step of causing a reaction gas containing oxygen and sulfur to react with the sintered body. A heat treatment time in the heat treatment step is 1 hour or more and 50 hours or less.