Spinel Single-Crystal Growth With Curved Heat-Shield Slit Heating
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Solution Overview
Problem
Existing growth methods for magnesium aluminate spinel crystals, such as the flux method, Verneuil's method, and the Czochralski method, result in defects like inclusions and cores due to the high volatilization of MgO and Al2O3 at high temperatures, leading to poor crystal quality and small sizes, which hinder practical applications.
Innovation Solution
A growth method using the edge-defined film-fed growth technique, involving specific arrangements of heat shields and temperature gradients, along with controlled seeding, necking, and widening processes, to enhance crystal growth quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional growth methods (flux method, Verneuil's method, Czochralski method) are used to grow magnesium aluminate spinel crystals, then crystal growth can be achieved, but serious non-proportional volatilization of MgO and Al2O3 occurs at high temperature, causing defects like inclusions and poor crystal quality
Solution Approach 1:
The patent applies inert atmosphere by conducting the crystal growth process in a vacuum environment or inert gas atmosphere. This prevents the volatilization of MgO and Al2O3 by eliminating oxygen and reactive gases, thereby avoiding the formation of harmful inclusions and maintaining crystal quality during high-temperature growth
Solution Approach 2:
The patent changes the growth parameters by using a specific temperature range (2130-2200°C) and controlling the atmosphere conditions. By optimizing these parameters, the patent achieves proportional volatilization prevention and improves crystal quality while maintaining successful crystal growth
2Productivity
If high temperature (2130-2200°C) is used to melt raw materials for crystal growth, then crystal growth can be achieved, but non-proportional volatilization occurs causing inclusions and poor crystal quality
Solution Approach 1:
The patent uses vacuum or inert gas atmosphere during high-temperature melting and growth processes. This prevents oxidative volatilization of MgO and Al2O3, ensuring that high temperature processing does not lead to poor crystal quality or inclusions, thus maintaining both productivity and reliability
3Ease of manufacture
If conventional growth methods are used, then crystal growth can be achieved, but defects such as bubbles, inclusions, and growth striations are produced
Solution Approach 1:
The patent employs vacuum or inert gas atmosphere throughout the growth process to prevent oxidation and volatilization. This creates a clean growth environment that eliminates bubbles and inclusions, achieving high manufacturing precision while keeping the process manageable
Solution Approach 2:
The patent optimizes growth parameters including temperature (2130-2200°C), atmosphere composition, and growth rate to minimize defects. By carefully controlling these parameters, the patent achieves uniform heating and reduces growth striations, improving manufacturing precision
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 reduces defects such as bubbles, inclusions, and growth striations, resulting in high-quality, large-sized magnesium aluminate spinel crystals with improved mechanical and physical properties.
Implementation Method 1
an upper heat shield and a lower heat shield are arranged above the mold, and a cross section of a slit between the upper heat shield and the lower heat shield is a curved surface
Implementation Method 2
raising the temperature of the crystal growth furnace to 2130-2200° C., so that the crystal growth raw materials are melted
Implementation Method 3
making the seed crystals contact a top end of a seam of a mold, and then pulling the seed crystals so that the crystal growth raw materials condense and grow on the seed crystals
Implementation Method 4
vacuuming the crystal growth furnace and then filling with inert gas
Implementation Method 5
after the end of crystal growth, starting annealing to cool down
Data Source
AI summary
The present application provides a growth method for single crystals of magnesia-alumina spinel by an edge-defined film-fed growth technique, comprising: putting seed crystals and crystal growth raw materials into a crystal growth furnace; vacuuming the crystal growth furnace, filling with inert gas, heating and melting the crystal growth raw materials; making the seed crystals contact a top end of a seam of a mold, pulling the seed crystals, shouldering, making crystals grow, and annealing to cool down after crystal growth. An upper heat shield and a lower heat shield are arranged above the mold, and a cross section of a slit between the heat shields is a curved surface. The cross section of the slit between the heat shields is controlled as a curved surface, so that the present application achieves the effect of uniform heating of the single crystals of magnesia-alumina spinel in an upward pulling process.