XIONG wenting ^{1, 2}, YUAN Qinjian ¹, LI Yingying ², DONG Yanze ²

(1. School of Information Management, Nanjing University, Nanjing 210023, Jiangsu, China;

2. Jingdezhen Ceramic University, Jingdezhen 333403, Jiangxi, China)

Extended abstract:

[Significance] Piezoelectric materials occupy an important position in the field of functional materials, due to their excellent electromechanical energy conversion properties. In the early 21st century, lead-based piezoelectric materials, such as PZN-PT, PMN-PT and PMN-PZ-PT, emerged, but their lead content exceeded 60%, and the high-temperature sintering released toxic vapors that harmed health and the environment. Driven by EU bans (such as RoHS) and global environmental strategies, the development of lead-free alternatives has become an urgent need. However, their energy efficiency and stability still need improvement, preventing their industrialization. Furthermore, the rise of the flexible electronics industry has spurred the development of piezoelectric materials, such as PVDF polymers and thin films. However, while polymers offer high flexibility, their piezoelectric coefficients are relatively low, and the complex fabrication process and poor compatibility with MEMS limit the widespread application of thin films. Therefore, novel composite materials combining high-performance piezoelectric ceramics with flexible polymers have attracted considerable attention.

[Progress] The development of eco-friendly lead-free piezoelectric materials has become an imperative trend to supersede traditional lead zirconate titanate based materials. However, critical challenges persist, regarding energy conversion efficiency and cyclic stability. Based on global patent data in the past two decades, this study was aimed to provide a comparative analysis of technological progress in China, the United States, Japan, the Republic Korea and Germany, across the dimensions of innovation entities and technological hotspots. It is demonstrated that China and Japan possess prominent competitive advantages in the research and development of piezoelectric materials. In terms of material systems, innovation hotspots are concentrated on compositional optimization, nanoscale dimensions and crystal structure modulation of lead-free and composite materials. Regarding device applications, technologies, such as precision structural arrays, multilayered structures and piezoelectric patterning, are driving the evolution of components toward integration, miniaturization and flexibility. These advancements are aimed to satisfy the rigorous requirements of nanogenerators, intelligent robotics, wearable devices and biomedicine.

[Conclusions and prospects] The global piezoelectric materials field is undergoing a profound transformation from "fundamental research and development" to "full-chain layout". Foreign companies are gradually shifting their innovation focus from basic materials to integrated piezoelectric components and extending to downstream applications, with a particular emphasis on piezoelectric components, such as stacked piezoelectric devices, ultrasonic transducers, piezoelectric vibrators, sound generators and RF filters. Novel materials are focused, such as piezoelectric films, polymers and composites, while a patent strategy was also emphasized, covering the entire "materials-devices-applications" chain. In the future, industry-academia-research collaboration in piezoelectric technology should focus on four dimensions, i.e., material composites, green manufacturing processes, intelligent innovation and precise applications. Key challenges need to be overcome in the large scale preparation of polymer/fiber-piezoelectric ceramic composite systems and multi-element lead-free materials. The introduction of AI driven intelligent manufacturing systems, utilizing machine learning for molecular design, performance prediction and process parameter optimization, will be expected to achieve a paradigm shift in models and shorten the cycle from development to application of new materials. Simultaneously, adhering to green and sustainable development requirements, technological innovation in low-temperature sintering and material recycling should be accelerated. For final applications, the market trends include 5G/6G communication, biomedicine, 3D printing, automotive electronics, Internet of Things and smart wearables, while the advancement of components are promoted, such as tactile vibrators, ultrasonic transducers, acoustic sensors and Internet of Things sensors, towards high frequency precision, high integration and thinness and flexibility, thus openning up a closed loop of technology transformation from materials to devices to applications.

Key words: piezoelectric materials; patent analysis; lead-free; technology hotspots; industry academia research collaboration