Amorphous Doped Titanium Oxide Low-E Coating Thermal Stability
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Solution Overview
Problem
Conventional low-E coatings using titanium oxide are not thermally stable after heat treatment, leading to film crystallization and thermal stress, which deteriorates the performance of the coating stack.
Innovation Solution
A low-E coating with a high refractive index doped titanium oxide layer, deposited in an amorphous or substantially amorphous state, using sputter-deposition in an oxygen-depleted atmosphere to maintain stability during heat treatment, incorporating elements like ZnSn, Ba, and others to enhance thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional titanium oxide layers are sputter-deposited to achieve a crystalline structure, then the refractive index is improved, but thermal stability deteriorates due to film crystallization and thermal stress during heat treatment
Solution Approach 1:
The patent changes the deposition parameters by sputter-depositing titanium oxide in an oxygen-depleted atmosphere (low oxygen partial pressure) to obtain an amorphous structure with high refractive index that remains stable during heat treatment, avoiding the conventional approach of creating crystalline structures that cause thermal stress
Solution Approach 2:
The patent creates a composite low-E coating structure combining amorphous high-index titanium oxide layer with infrared-reflecting metal layers (silver, aluminum, or their alloys), where the amorphous titanium oxide provides both high refractive index and thermal stability without causing stress to adjacent layers
2Temperature
If heat treatment is applied to the low-E coating, then the glass substrate is tempered, but the titanium oxide layer crystallizes causing thermal stress that deteriorates coating performance
Solution Approach 1:
The patent performs preliminary action by depositing the titanium oxide layer in an amorphous state through sputter-deposition in oxygen-depleted atmosphere before heat treatment, so that the layer is pre-configured to withstand subsequent heat treatment without crystallization-induced stress
Solution Approach 2:
The patent uses an oxygen-depleted (inert) atmosphere during sputter-deposition to prevent oxidation and crystallization of the titanium oxide layer, creating an amorphous structure that remains stable during subsequent heat treatment processes
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 amorphous doped titanium oxide layer ensures thermal stability and improved performance of the low-E coating, maintaining optical and thermal properties post-heat treatment, suitable for applications in monolithic and insulating glass window units and vehicle windows.
Implementation Method 1
The doped titanium oxide layer(s) is designed and deposited in a manner so as to be amorphous or substantially amorphous (as opposed to crystalline) in the low-E coating
Data Source
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AI summary
A coated article includes a low emissivity (low-E) coating having at least one infrared (IR) reflecting layer of a material such as silver, gold, or the like, and at least one high refractive index layer of or including titanium oxide and at least one additional metal. A doped titanium oxide layer(s) is designed and deposited in a manner so as to be amorphous or substantially amorphous (as opposed to crystalline) in the low-E coating, so as to better withstand optional heat treatment (HT) such as thermal tempering and reduce haze. The high index layer may be a transparent dielectric high index layer in preferred embodiments, which may be provided for antireflection purposes and/or color adjustment purposes, in addition to having thermal stability.