Lithium Aluminum Silicate Glass Ceramic Brightness Control
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Solution Overview
Problem
Current transparent lithium aluminum silicate (LAS) glass ceramics face challenges in achieving low color, high brightness, and low scattering while maintaining favorable manufacturing properties, including short ceramization times and economical production, due to issues with nucleating agents like TiO2 and SnO2, which lead to unwanted color complexes and scattering.
Innovation Solution
A crystallizable lithium aluminum silicate glass composition with specific oxide content ratios, including Li2O, Al2O3, SiO2, TiO2, ZrO2, SnO2, and MgO, optimized to minimize color and scattering, and enhance brightness, with controlled ceramization processes to achieve desired properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If TiO2 and SnO2 are used as nucleating agents to achieve crystallization, then the glass ceramic can be produced with desired crystal structure, but color complexes form leading to increased color and reduced brightness
Solution Approach 1:
The patent modifies the chemical composition parameters by introducing specific ratios of Al2O3 (15-25 wt%), TiO2 (1-3 wt%), and SnO2 (0.1-1 wt%), along with controlling Fe2O3 content (0.01-0.1 wt%). This parameter optimization enables crystallization control while minimizing color complex formation, achieving brightness >80% and color c* < 4.
Solution Approach 2:
The patent creates a composite nucleating agent system combining TiO2 and SnO2 with controlled Al2O3 content. This composite approach allows synergistic crystallization enhancement while the specific composition ratios prevent excessive color complex formation, resolving the contradiction between crystallization control and brightness.
2Illumination intensity
If conventional refining agents like arsenic oxide are used to improve transparency, then brightness and low color are achieved, but safety and environmental protection are compromised
Solution Approach 1:
The patent replaces toxic arsenic oxide with tin oxide (SnO2) as the refining agent. SnO2 achieves similar or superior refining effectiveness with better safety and environmental properties. The controlled SnO2 content (0.1-1 wt%) ensures effective bubble removal while maintaining brightness and color characteristics without the harmful effects of arsenic.
Solution Approach 2:
The patent converts the potentially harmful effect of SnO2 (which can cause color complexes) into a benefit by precisely controlling its content and combining it with Al2O3 and TiO2. This optimized composition uses SnO2's refining capability while minimizing its negative optical effects, achieving both safety improvement and optical quality.
3Reliability
If higher SnO2 content is used to ensure sufficient refining, then bubble quality improves, but color complexes increase leading to higher color and lower brightness
Solution Approach 1:
The patent identifies and optimizes the critical parameter of SnO2 content, setting it within 0.1-1 wt%. This precise parameter control ensures adequate refining effectiveness for bubble quality while preventing excessive color complex formation. The optimized SnO2 level, combined with Al2O3 (15-25 wt%) and TiO2 (1-3 wt%), achieves the desired balance.
Solution Approach 2:
The patent applies different functional concentrations to different components: high Al2O3 (15-25 wt%) for structural stability and color control, moderate TiO2 (1-3 wt%) for nucleation, and controlled SnO2 (0.1-1 wt%) for refining. This local optimization of each component's concentration achieves both bubble quality and optical properties.
4Illumination intensity
If Fe2O3 content is reduced to minimize color, then brightness improves, but manufacturing cost increases due to higher raw material requirements
Solution Approach 1:
The patent optimizes Fe2O3 content to a specific range of 0.01-0.1 wt%, which is low enough to maintain brightness (>80%) and color (c* < 4) but high enough to be economically manufacturable. This parameter optimization balances optical quality with manufacturing feasibility, avoiding the need for excessively expensive ultra-low iron raw materials.
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 optimized glass ceramic exhibits high brightness (>83%) and low color (c* ≤ 4) with minimal scattering, meeting the requirements for applications like fire protection and cooking surfaces, while allowing for short ceramization times and economical production.
Implementation Method 1
Both of these qualities imply low absorption, since the absorption bands, depending on their position in the visible spectrum, can both decrease brightness and increase color.
Implementation Method 2
Another essential characteristic of LAS glass-ceramics is scattering, which is determined by the size of the crystals, their birefringence, and the difference in refractive indices between the crystals and the residual glass.
Implementation Method 3
The thermal expansion behavior is generally optimized so that the materials exhibit very low expansion, usually α 20/700
Implementation Method 4
their low coefficient of thermal expansion combined with high resistance to temperature differences and thermal shock
Implementation Method 5
The crystallizable lithium aluminum silicate glass is transformed into a glass-ceramic through controlled crystallization (ceramization) in a subsequent temperature process.
Data Source
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AI summary
The invention relates to a crystallizable lithium aluminum silicate glass for the production of transparent glass ceramics, containing the following components (in wt.% on an oxide basis): Li₂O 3-5, Al₂O₃ 19-24, SiO₂ 62-70, TiO₂ >1.6-2.8, ZrO₂ 1-2.5, MgO 0.01-<0.5, SnO₂ 0.01-<0.15, subject to the condition (both in wt.%): 0.005 < MgO × SnO₂ < 0.06 (condition B1a). The invention also relates to the glass ceramic produced from this glass and its uses.