Mass Producible Transparent High-performance Piezoceramics through Pressureless Sintering

Abstract

Piezoelectric materials have been fundamental to technological innovation, enabling progress in various applications including sensors, actuators, energy harvesters, and ultrasonic transducers, etc. As decades of research bring the field to maturity, there is a growing demand for materials with new functionalities to meet the needs of next-generation technologies. Among these, transparency has emerged as a promising property, offering opportunities to expand the application scope of piezoelectric materials beyond traditional boundaries. Transparent piezoelectric ceramics combine optical and piezoelectric performance, enabling advanced applications such as transparent actuators, haptic touch-screen displays, and Transparent Ultrasound Transducers (TUT) for real-time, high-resolution imaging in medical applications through transparent interfaces. Despite their potential, transparent piezoelectric materials face significant challenges due to the inherent trade-offs between optical transparency and piezoelectric performance. Current transparent piezoelectric materials exhibit insufficient piezoelectric properties or rely on hot-press sintering, which limits their scalability for industrial applications. To overcome these limitations, this research develops novel transparent piezoelectric ceramics using pressureless sintering methods and advanced compositional modifications. This study investigates two material systems: La, Sm co-doped 0.71Pb(Mg1/3Nb2/3)O3–0.29PbTiO3 (PMN–0.29PT) and 0.4Pb(Mg1/3Nb2/3)O3–0.22PbZrO3–0.38PbTiO3 (PMN-PZ-PT) ceramics. The PMN–0.29PT composition achieves over 60% optical transparency and a high piezoelectric coefficient (up to 1104 pC/N), making it ideal for transparent actuators and high-resolution medical imaging. However, the low depolarization temperature (Td) of PMN–0.29PT increases the risk of depolarization in devices, where self-heating during operation can cause performance degradation. Addressing this challenge became the motivation for developing a second material system: La, Sm co- doped PMN-PZ-PT. This composition achieves over 50% transparency at room temperature, combined with a high piezoelectric coefficient (d33) of approximately 620 pC/N and an electromechanical coupling factor (kp) exceeding 0.6. Unlike pure PMN-PZ-PT, which exhibits significant property degradation near its depolarization temperature (Td), the La, Sm co-doped PMN-PZ-PT composition demonstrates excellent thermal stability. After thermal annealing at 150°C, it retains a d33 of approximately 600 pC/N and a kp of around 0.5, highlighting its enhanced resilience under elevated temperature conditions. These enhanced properties make the material a promising candidate for a wide range of industrial applications, particularly in fields that require a combination of high piezoelectric performance and thermal stability at elevated temperatures. These advancements bridge the gap between optical transparency and piezoelectric performance while ensuring scalability for industrial production. This work establishes a transformative approach to next- generation transparent piezoelectric materials, providing a foundation to meet the demands of advanced technological applications.