Life cycle assessment of lead-free potassium sodium niobate versus lead zirconate titanate: Energy and environmental impacts

Over the years, lead-based piezoelectric ceramics found extensive use in vital fields such as sensors and actuators. Despite their exceptional electromechanical properties, lead-containing materials pose severe environmental risks and foster a new era of lead-free piezoelectric materials after decades of research. However, recent comparative assessments of potassium sodium niobate (KNN) versus lead zirconate titanate (PZT) piezoelectric materials proposed that the environmental damage already presented before use due to raw material extraction and processing, invoking concerns on the true greenness of the lead-free alternatives. Nevertheless, many other factors deserve further consideration, for example, reference geometry and life cycle stage. Herein, the comprehensive life cycle assessment is undertaken on PZT and KNN-based ceramics with a unit volume of 0.001 m³ from cradle to gate. Results show that PZT exhibits higher negative impacts than KNN-based counterparts, attributed to lead extraction, processing, and associated environmental emissions. Across primary quantitative impact indicators from toxicity, environmental, and resource aspects, KNN-based ceramics impose fewer risks on the environment and human health, with the overall impact being only 28% of PZT ceramics. Still, more efficient methods are required for KNN-based ceramics to reduce the high energy consumption and emission during extraction and purification of raw material Nb₂O₅. This work not only offers critical insights for material development but also serves as a multifaceted reference for advanced fabrication technologies.