Scientists Achieve Breakthrough in Piezoelectric Thin Films with Record-Breaking Performance

An international team of researchers led by Professor Lam Yeng Ming (NTU MSE) and Dr Liu Huajun (IMRE, A*STAR) has made a significant breakthrough in achieving the highest performance in piezoelectric thin films. Lin Baichen, a PhD student co-supervised by Prof Lam and Dr Liu, is the leading first author of the study published in Nature. The team demonstrated a novel strategy that significantly enhances the electromechanical response in sodium niobate (NaNbO3, NNO) thin films by inducing extreme structural instability from competing antiferroelectric (AFE) and ferroelectric (FE) orders. 

Piezoelectric materials, which can convert mechanical energy into electrical energy and vice versa, are essential components in various applications, such as sensors, actuators, and medical imaging devices. The performance of these devices is primarily determined by the electromechanical coupling of the piezoelectric materials, characterised by the piezoelectric coefficient. The team showed that by engineering the coexistence of AFE and FE phases in NNO thin films through epitaxial growth and symmetry engineering at room temperature, they could achieve effective piezoelectric coefficients (d*33,f) exceeding 5,000 pm/V and an electric-field-induced strain of about 2.5% at room temperature. This result surpasses the previous record by an order of magnitude. The response was even higher at lower frequencies, reaching up to 18,400 pm/V with a strain of 9.2%.

"Harnessing competing AFE-FE phase transitions to achieve ultrahigh electromechanical response is a new strategy that goes beyond the conventional approaches based on morphotropic phase boundaries or nanoscale structural heterogeneity. This expands the toolbox for engineering piezoelectric materials," said Professor Lam, the study's co-corresponding author.

 

The ultrahigh piezoelectric response in the NNO films is attributed to the reduced energy barrier between AFE and FE phases and the significant polarisation change during the electric-field-induced AFE-FE phase transition. First-principles calculations and phase-field simulations provided valuable insights into the underlying mechanism, revealing domain-switching dynamics and interphase boundary motion during the phase transition. The study provides a deep understanding of the physical principles at play and contributes to developing a new class of high-performance piezoelectric materials.

 

The team's breakthrough is expected to stimulate global research efforts focused on exploiting antiferroelectric-ferroelectric phase competitions for high-performance piezoelectric. The implications of the research findings are far-reaching, promising advancements in microelectromechanical systems (MEMS), sensors, actuators, and energy harvesters. The potential for achieving such a high electromechanical response in thin films opens up exciting possibilities for miniaturised, high-performance devices. Moreover, the research holds promise for developing lead-free piezoelectric materials, addressing the environmental concerns associated with lead-based piezoelectrics. The development of lead-free materials with exceptional electromechanical properties is crucial for sustainable and eco-friendly technologies.

 

Lin, B., Ong, K.P., Yang, T. et al. "Ultrahigh electrochemical response from competing ferroic orders" Nature (2024). DOI: https://doi.org/10.1038/s41586-024-07917-9