Scientists in Japan have created a new material that could someday replace toxic components in many electronic devices. With growing concern over the disposal of cell phones, computers, and other gadgets containing hazardous materials, the team proposes that its discovery will render future devices less harmful to the environment.
The innovation is a type of piezoceramic—a material that shrinks or swells when an electric field is applied. The ringers in cell phones, for instance, are made from piezoceramics that vibrate at high frequencies in response to an electric signal. The effect also works in reverse—squeeze a piezoceramic, and it generates an electric field. That produces a spark in a barbecue igniter, for instance. Sonar systems, fuel injectors, and many sensors also rely on these shape-changing materials.
Today, the most widely used piezoceramic is lead zirconium titanate (PZT). “It’s the material of choice,” says Harry Tuller of the Massachusetts Institute of Technology. It’s also an environmental headache. Lead contributes 60 percent of the weight of PZT.
According to the New York–based environmental-research firm INFORM, consumers in the United States will collectively own some 500 million cell phones by 2005. Once discarded, these devices could release a total of 312,000 pounds of lead into the environment.
Countries in Europe and Asia are already adopting laws that require companies to recycle the electronic products they manufacture. Also, several programs in the United States have begun to collect cell phones and recycle their parts.
To tackle the problem at its source, researchers around the world have developed a number of leadfree piezoceramics, “but none as good as PZT,” says Tuller. “That’s been difficult to achieve.”
Now, scientists at the Toyota R&D Laboratories in Nagakute and at the DENSO Corp. in Kariya report creating a new piezoceramic that’s not only leadfree but in preliminary tests matches PZT’s performance. “This is the best leadfree [piezoceramic] that I’ve seen,” says Susan Trolier-McKinstry of Pennsylvania State University in State College. “It’s pretty exciting.”
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The material is an alkaline niobate–based ceramic—a polycrystalline material containing mostly niobate, sodium, and potassium, along with minor amounts of lithium, tantalum, and antimony. The researchers engineered the material so it doesn’t heat up after going through repeated cycles of shape changing. Thermal stability is required to ensure long-term stability of piezoceramics, says Trolier-McKinstry.
The Toyota and DENSO researchers describe their innovation in the Nov. 4 Nature. Coauthor Yasuyoshi Saito of Toyota says that he doesn’t know when the new material might find its way into electronic devices. The researchers still need to resolve several technical issues related to mass production, he says.