A review on lead-free piezoelectric ceramic sensors for sustainable and intelligent applications

Lead zirconate titanate (PZT) has long been regarded as the gold standard material for piezoelectric sensors owing to its outstanding piezoelectric performance ( d 33 = 500–600 pC/N) and well-established industrial scalability. However, its environmental toxicity, limited mechanical flexibility, and instability under extreme conditions make it less suitable for wearable electronics, biomedical implants, and high-temperature sensing. These limitations have spurred intensive efforts to develop lead-free ceramic piezoelectric materials as more sustainable and versatile alternatives. Recent advancements in this field highlight the increasing potential of lead-free systems to rival or even surpass conventional PZT-based devices. This review systematically explores the latest progress in lead-free piezoelectric materials, focusing on two major directions: the formulation of alternative compositions such as potassium sodium niobate (KNN) and bismuth sodium titanate (BNT) that aim to achieve comparable performance metrics, and the development of intelligent sensing systems that offer enhanced sensitivity, broader operational temperature ranges, and mechanical adaptability. Rather than focusing solely on replacing toxic components, this review proposes a multidimensional evaluation framework that considers piezoelectric coefficients, dielectric properties, and mechanical compliance as equally critical parameters. Moreover, the integration of artificial intelligence (AI) is discussed as an emerging tool to accelerate the discovery and optimization of high-performance lead-free compounds. Looking ahead, the field is anticipated to move toward the realization of intelligent, flexible, and multifunctional sensing platforms for use in self-powered systems, harsh environments, and advanced energy harvesting technologies, signifying a crucial shift toward sustainable piezoelectric device innovation.