Sealing Glass: Uses and Applications in Industry

What Makes Sealing Glasses so Useful?
Using glass as a sealing material has many benefits, including the fact that it is possible to tune its coefficient of thermal expansion (CTE) during production. Because many materials expand when heated, having two sealed components expand at different rates means that the seal between them can be compromised.

The thermal expansion coefficient of sealing glasses can be made to match that of a range of different engineering materials by adjusting the manufacturing and composition parameters. This means that when components undergo thermal expansion, the glass seals remain sealed.

Sealing glasses have widespread use because of this property. The material is used especially in the production of reed switches, electric discharge tubes, vacuum tubes, and other electronic components, as well as in other glass-to-metal applications.

Specialized sealing glasses can be made to have other desirable properties, including the ability to be laser-bonded, stability under thermal cycling, and resistance to chemical attack. Below, this article will explore some of the high-spec applications for which these characteristics render sealing glasses suitable.

Solar Cells
There has been significant attention in recent years being paid to a class of minerals with an ABX3 structure known as perovskites as these may be an alternative to silicon in photovoltaic cells.1

The material promises both high photovoltaic efficiency and low manufacturing costs, and worldwide efforts are underway to commercialize them.

Exposing perovskites to even small amounts of moisture can cause complete loss of functionality, which is one of the issues facing the development of perovskite solar cells. It is therefore essential to hermetically encapsulate perovskites, both to prevent lead-containing chemicals from leaking out and to prevent moisture from getting into the cell.

Using sealing glasses to encapsulate perovskite photovoltaic elements can ensure that they remain completely sealed from the external environment.

Perovskite crystals can be protected from moisture incursion and have their lifetime drastically increased using laser-assisted bonding of glass frit, additionally ensuring long-term hermetic encapsulation.2

Long-term stability of the entire cell is ensured by matching the thermal expansion coefficient of the surrounding materials to that of the glass.

Metal Ion and Thermal Batteries
The battery industry has been undergoing radical changes as it adapts to a wider transition towards renewable energy sources and increased demand for more compact and efficient energy storage solutions such as those used in electric cars.

For both commercial and experimental battery technologies, sealing glass plays a vital role. The current go-to for renewable energy storage applications and electric vehicles are lithium-ion (Li-ion) batteries, which require hermetic seals that exhibit long-term stability at high temperatures and resistance to chemical attack.

This is also true of sodium-ion (Na-ion) batteries, which are currently being investigated as a low-cost alternative to lithium-ion technology.

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