Abstract: Relaxor ferroelectric single crystals have important applications in medical ultrasound transducers, hydroacoustic devices and other fields due to their excellent piezoelectric properties. The relaxor ferroelectric single crystals grown by the Bridgman method inevitably suffers from component segregation, resulting in extremely low utilization. In this work, the variation of piezoelectric coefficient (d₃₃) and dielectric constant (ε₃₃^T/ε₀) of 0.24PIN-0.46PMN-0.30PT ferroelectric single crystals along the growth direction were tested. The results show that d₃₃ and ε₃₃^T/ε₀ are extremely variable along the growth direction, with less than 20 mm of the region maintaining close performance. Polarization modulations were applied in different regions with close ferroelectric-ferroelectric phase transition temperatures through different polarization designing. The d₃₃ and ε₃₃^T/ε₀ of more than 60% region of the crystalline maintain in the range of (1 500±140) pC·N^-1 and 4 900±350, respectively. In order to verify the consistency of the resonance peaks of the crystal after polarization modulation, the resonance spectra of the k₃₃ vibrators in the two end regions were tested. The results show that the electromechanical coupling coefficients are close to each other, and the peak positions of resonance and anti-resonance are also close to each other. Importantly, there don’t exist additional spurious-mode vibrations. These demonstrate the feasibility of employing polarization modulation to regulate the uniformity of the PIN-PMN-PT ferroelectric single crystals along the growth direction. This work provides a reference solution to improve the utilization of PIN-PMN-PT ferroelectric single crystals.

Key words: PIN-PMN-PT, ferroelectric single crystal, polarization modulation, component segregation, piezoelectric coefficient