Advances in research on high-Curie temperature BiFeO₃-based ceramics

Piezoelectric materials are functional materials that can realize electromechanical coupling characteristics and are widely used in electronic information, sensors, ultrasonic transducer, nondestructive testing, and communication technology. However, the current dominant piezoelectric ceramics are lead zirconium titanate systems. These systems contain lead, which is a toxic element, and the content of lead oxide or lead tetroxide in lead-based piezoelectric ceramics is over 60%. Because of the volatile and water-soluble characteristics of lead, the production and disposal of traditional lead-based piezoelectric ceramics will result in different levels of lead pollution, which will severely harm the environment and human health. With the improvement of environmental protection and the sustainable development of human society, the harmful effects of lead-based piezoelectric ceramics have aroused increasing attention. Countries around the world have introduced legislation to ban or restrict the use of lead-based ceramics. Thus, lead-free piezoelectric ceramics have received much attention because they are environment-friendly and pollution-free. In the last decade, countries worldwide invested a large amount of funds and labor to search and develop environment-friendly lead-free piezoelectric ceramics, which can be used to replace lead-based piezoelectric ceramics in actuators, transducers, and sensors. In recent years, BiFeO₃-BaTiO₃ (BF-BT) lead-free solid solutions, which are considered as one of the most promising candidates for high-temperature piezoelectric applications, have received extensive attention from researchers because of their high-Curie temperature (T_C) and large spontaneous polarization (P_s), as well as high piezoelectric coefficient (d₃₃). This paper mainly reviewed recent advances in BF-BT ceramics, including the phase structure and piezoelectric property, as well as the magnetic property. In addition, the problems that need to be solved before these ceramics can be practically applied were also analyzed according to the knowledge of the authors.