Mullite Crucible with Silica Lining for Silicon Crystal Growth
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Solution Overview
Problem
Conventional vitreous silica crucibles used for silicon crystal manufacturing lack sufficient high-temperature strength and are costly to produce, with existing reinforcement methods being laborious and prone to impurity contamination.
Innovation Solution
A composite crucible made of mullite material with a transparent vitreous silica layer on its inner surface, providing enhanced high-temperature strength and preventing impurity contamination, while being more cost-effective and durable.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional vitreous silica crucibles are used for silicon crystal manufacturing, then the crucibles can be manufactured, but they lack sufficient high-temperature strength and are costly to produce
Solution Approach 1:
The patent applies composite materials by combining mullite (as the base material providing high-temperature strength) with vitreous silica (as the inner lining providing chemical inertness and preventing silicon contamination). This composite structure resolves the contradiction by achieving both high-temperature strength and cost-effectiveness, as mullite is cheaper than high-purity vitreous silica while providing the necessary mechanical strength at operating temperatures.
Solution Approach 2:
The patent applies local quality by providing different material properties to different parts of the crucible: the outer body is made of mullite for structural strength and heat resistance, while the inner surface is lined with vitreous silica for chemical compatibility with silicon melt. This localized differentiation allows each material to perform its optimal function, resolving the contradiction between strength and cost.
2Strength
If reinforcement methods are applied to conventional crucibles, then high-temperature strength is improved, but the processes become laborious and prone to impurity contamination
Solution Approach 1:
Instead of applying complex reinforcement methods to conventional crucibles, the patent uses a composite material structure where mullite and vitreous silica are combined in a way that provides inherent high-temperature strength. This eliminates the need for complex reinforcement processes, reducing manufacturing complexity while achieving the desired strength improvement.
Solution Approach 2:
The patent changes the fundamental material parameters by using mullite (with specific composition of Al2O3 and SiO2 in 3:2 ratio) instead of conventional vitreous silica. This parameter change provides inherent high-temperature strength without requiring complex reinforcement processes, simplifying manufacturing while improving strength.
3Ease of manufacture
If conventional vitreous silica crucibles are used, then manufacturing is straightforward, but impurity contamination occurs during long-term high-temperature use
Solution Approach 1:
The patent applies local quality by lining the inner surface with vitreous silica, which provides chemical inertness and prevents impurity contamination of the silicon melt. The outer mullite body provides structural strength. This localized differentiation allows the crucible to maintain manufacturing simplicity while preventing contamination through the chemically inert inner lining.
Solution Approach 2:
The vitreous silica inner lining acts as an intermediary barrier between the silicon melt and the crucible body. This intermediary layer prevents direct contact between the melt and potential impurity sources in the crucible material, thereby preventing impurity contamination while maintaining manufacturing simplicity.
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 composite crucible enables long-term use at high temperatures with reduced impurity contamination and lower production costs, suitable for manufacturing silicon crystals for solar cells.
Implementation Method 1
a transparent vitreous silica layer formed on an inner surface side of the crucible body
Implementation Method 2
a crucible body made of mullite material whose main component is alumina and silica
Data Source
AI summary
The purpose of the present invention is to provide a crucible which has high viscosity at high temperature, and can be used for a long time, and can be manufactured at low cost, and a method of manufacturing the same. The composite crucible 10 is characterized in the use of mullite (3Al2O3.2SiO2) as the basic material of the crucible. The composite crucible 10 has the crucible body 11 made of mullite material whose main component is alumina and silica, and a transparent vitreous silica layer 12 formed on the inner surface of the crucible body 11. The thickness of the transparent vitreous silica layer 12 is smaller than that of the crucible body 11. The crucible body 11 can be formed by the slip casting method, and the transparent vitreous silica layer 12 can be formed by the thermal spraying method.