Potassium: The Facilitator of the Periodic Table | Playing a Key Role in Ion-Exchange | Corning

Potassium: The Facilitator

Potassium: The Facilitator

Potassium is an ingredient in many of Corning’s technical glasses.  For example, it plays a key role in the ion-exchange process that helps give Corning® Gorilla® Glass its toughness.  But Dr. Adam Ellison, technology delivery officer for Corning Glass Technologies, has been intrigued by potassium since his graduate school days, when he made a discovery that defied conventional wisdom about how glasses are structured.

Sodium is often the atom of choice when people are trying to describe the structure of a glass that contains alkali. Many scientists assumed that elements in the same family – e.g., potassium, lithium, rubidium, cesium – would behave the same way. However, Ellison discovered that’s not true. “Potassium is so big that other atoms have to organize themselves around it,” he explains.

But potassium is no bully. In fact, it’s more of a mediator or facilitator. One of the most interesting behaviors that Ellison observed is that potassium will make elements cooperate when they would normally conflict. It does this in two key ways. If an element is difficult to dissolve, adding potassium will help by both increasing the solubility and the amount you can dissolve at a given temperature. The addition of potassium also lowers the temperature at which silica devitrifies, which creates more flexibility.

“When you’re trying to put something in the glass that the main glass components just don’t want in there, potassium is magical,” says Ellison.

Ellison discovered this unusual behavior when he was conducting research for his Ph.D., examining how the solubility of zirconium oxide and titanium oxide varied with the composition of the glass. Because he was building on research done by his advisor’s previous students, he was working with a base glass containing potassium oxide, aluminum oxide, and silicon oxide. Ellison observed an extremely strong link between the amount of potassium oxide and solubility. And when he conducted further experiments, he noted that the behavior of the glass was relatively insensitive to other variables.

It’s knowledge that Ellison has taken advantage of to develop new technical glass compositions for Corning.

“Potassium actually shows up in Corning’s archive of technical glasses going back as far as I can find records,” Ellison says. “But with our earlier efforts, we didn’t have a real understanding of the arrangements of atoms in glasses, so a lot of work was being done on intuition or serendipity. Today, our use of potassium is informed by a lot of understanding.”

The implications are enormous.  In the Silicon feature, we noted that Corning has the potential to use the entire periodic table in nearly limitless combinations. Potassium, as a great facilitator, helps make that possible.

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