Lead-Free Piezoelectric Ceramics: Ba-Modified Bismuth Sodium Titanate (BNBT) for High-Frequency Applications

BNBT ceramics with the MPB composition (x=0.06∼0.07) exhibit a rhombohedral (Fα)-tetragonal (Fβ) morphotropic phase boundary (MPB), as confirmed by X-ray data, as well as by their dielectric and piezoelectric properties. These ceramics are considered to be a promising alternative to lead-based piezoelectric materials due to their lead-free nature.

The MPB composition of BNBT ceramics offers several advantages in high-frequency ultrasonic applications and as piezoelectric actuator materials. Firstly, they exhibit a lower free permittivity (ε33T/ε0), which means that they can store and release electrical energy more efficiently. This characteristic is particularly desirable in high-frequency applications where rapid energy conversion is required.

Additionally, BNBT ceramics with the MPB composition possess a high electromechanical coupling factor (kt or k33). This factor represents the ability of the material to convert electrical energy into mechanical motion and vice versa. The high coupling factor of BNBT ceramics allows for efficient transduction between electrical and mechanical signals, making them suitable for various actuation applications.

Moreover, these ceramics demonstrate high mechanical strength, making them durable and reliable in demanding operational conditions. This mechanical robustness is crucial for piezoelectric materials used in actuator applications, where they need to withstand repeated stress and strain without degradation.

In summary, the BNBT ceramics with the MPB composition (x=0.06∼0.07) possess advantageous dielectric and piezoelectric properties, making them superior choices as lead-free piezoelectric ceramics in high-frequency ultrasonic applications and as piezoelectric actuator materials.