An alchemist’s dream: Lead-free electronics

Lead to be phased out

Lead, or more precisely lead oxide, can cause both acute and chronic health and environmental problems. European regulators have decided that the use of lead in electronics must be phased out. But finding a replacement for a lead-containing material called PZT, which is found in almost all electronics, has been an alchemist's dream. Researchers have mostly failed to find a good enough alternative that provides the same functionality. As a result, the electronics industry has been exempt from the ban.

A material called KNN has long been considered a possible alternative, but finding a manufacturing method that provides both the right material properties and is industrially feasible has proved problematic. A group of researchers led by Tor Grande at NTNU's Department of Materials Science have solved both problems.

Lead everywhere

The most common leaded material in today's electronics (PZT) generates an electrical voltage when exposed to pressure. It is used in "gadgets" where mechanical movement has to be transformed into an electrical signal, or vice versa. You'll find PZT in your mobile phone, your car, your computer -- in short, everywhere where there are sensors and displays. Ultrasound images would not be possible without these kinds of materials.

Over the past ten years, there has been tremendous growth in research on lead-free alternatives. A type of material called alkali niobate, also known as KNN, is considered a likely successor. However, KNN poses two main problems that have been difficult to resolve: one is finding a KNN variant that has the exact properties needed for electronics. The second is to develop a method for industrial production of the material. NTNU researchers have developed an approach that is ready for patenting. "I had a theory and some ideas, and I knew that there would be something exciting out of this, I just did not know exactly what," says Grande, who is the research project manager. Grande thinks it is very satisfying to create an environmentally friendly alternative to PZT.

Grande uses a kitchen analogy when he explains the trick behind the new method. Microscopic ingredients are baked, rolled out and cooked in thin ceramic sheets. But the secret is the highly precise structure of the ceramic sheet, which has a texture that helps transform mechanical pressure into electrical signals, and vice versa. This gives the sheet the exact same properties as PZT.

"The method we have developed kills two birds with one stone," says Grande. "Not only can we adjust the process to create properties in the ceramic sheet that are precisely suited to different electronics -- we can also scale up the process so that we can produce almost unlimited amounts of it."

Green electronic products?

The team has submitted a patent application and is now working on verification and further development. "If we succeed, it will be of great commercial interest," Grande says. "I will be surprised if this product doesn't take over a significant part of the market in ten years. Maybe this will help in the creation of green electronic products?"