Nuclear Research Institute Develops 'Eco-Friendly' Lead-Free Piezoelectric Composite Materials

The Korea Atomic Energy Research Institute (hereinafter KAERI) announced on the 28th that a research team led by Senior Researcher Park Gyu-hyun and Principal Researcher Lee Min-gu from the Instrument Safety Diagnosis Research Division has succeeded in developing eco-friendly lead-free piezoelectric material technology.

(From left) Min-gu Lee, Principal Researcher, Safety Diagnosis Research Division; Kyuhyun Park, Senior Researcher. Provided by Korea Atomic Energy Research Institute

Piezoelectric materials generate electricity when pressure is applied and are widely used in industries such as sensors and semiconductors.

Until now, lead titanate zirconate has been the primary piezoelectric material used. However, since lead is harmful to human health and the environment, its use is being globally restricted, leading to active research on eco-friendly lead-free piezoelectric materials. In this process, temperature instability has been a challenge for researchers to overcome.

The lead-free piezoelectric material technology developed by the KAERI research team is significant because it addresses this issue.

The research team solved the instability problem of existing lead-free piezoelectric ceramic materials, whose piezoelectric performance decreases or increases with temperature, by utilizing this phenomenon inversely. They created a laminated piezoelectric composite material by alternately stacking two materials that exhibit opposite piezoelectric performance changes with temperature.

First, the team stacked layers of potassium sodium niobate ((K,Na)NbO3, hereinafter KNN), whose piezoelectric performance decreases as temperature rises, and bismuth ferrite (BiFeO3, hereinafter BF), whose piezoelectric performance increases with temperature, to create the composite material.

Schematic diagram of the development principle of the 'stacked piezoelectric composite material' by the research team at the Korea Atomic Energy Research Institute. Provided by Korea Atomic Energy Research Institute

This composite material shows differences in temperature stability depending on the composite ratio. After numerous experiments, the team identified the optimal ratio of KNN material as 43%, and confirmed that at this ratio, the piezoelectric performance variation rate is maintained at a maximum of 4.7% up to 300℃.

This performance is more than twice as improved compared to the temperature stability of existing lead-free piezoelectric ceramic materials (based on a maximum of 100~150℃, with a piezoelectric performance variation rate within 10%), which KAERI emphasized as a world-class level.

The technology developed by the research team also enhanced piezoelectric performance. Most piezoelectric materials used at high temperatures of 300℃ previously had a bismuth layered structure (Bi-layered structure), with piezoelectric constants below 20.

In contrast, the team succeeded in increasing the piezoelectric constant to over 150 by using a perovskite structure with KNN and BF, achieving excellent piezoelectric performance even at high temperatures.

The piezoelectric material developed by the research team, with its excellent temperature stability and piezoelectric performance, is expected to be used in high-sensitivity sensors for high-temperature environments such as nuclear power plants, as well as various eco-friendly piezoelectric components and devices in the future.

The research results were published in the September issue of the international materials science journal, Journal of Materials Chemistry A.

Notably, the research team has completed domestic patent registration for the developed technology and is currently undergoing patent examination overseas in the United States, Europe, and other regions.

Park Tae-jin, head of the Instrument Safety Diagnosis Research Division at KAERI, said, “Special sensors used in harsh environments such as nuclear power plants have mostly relied on foreign technology until now. However, based on the research team’s results, we expect that eco-friendly domestic technology will be preferentially applied in the special sensor field in the future.”

This content was produced with the assistance of AI translation services.