Transparent piezoelectrics are highly desirable for numerous hybrid ultrasound–optical devices ranging from photoacoustic imaging transducers to transparent actuators for haptic applications^{1,2,3,4,5,6,7}. However, it is challenging to achieve high piezoelectricity and perfect transparency simultaneously because most high-performance piezoelectrics are ferroelectrics that contain high-density light-scattering domain walls. Here, through a combination of phase-field simulations and experiments, we demonstrate a relatively simple method of using an alternating-current electric field to engineer the domain structures of originally opaque rhombohedral Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ (PMN-PT) crystals to simultaneously generate near-perfect transparency, an ultrahigh piezoelectric coefficient d₃₃ (greater than 2,100 picocoulombs per newton), an excellent electromechanical coupling factor k₃₃ (about 94 per cent) and a large electro-optical coefficient γ₃₃ (approximately 220 picometres per volt), which is far beyond the performance of the commonly used transparent ferroelectric crystal LiNbO₃. We find that increasing the domain size leads to a higher d₃₃ value for the [001]-oriented rhombohedral PMN-PT crystals, challenging the conventional wisdom that decreasing the domain size always results in higher piezoelectricity^8,9,10. This work presents a paradigm for achieving high transparency and piezoelectricity by ferroelectric domain engineering, and we expect the transparent ferroelectric crystals reported here to provide a route to a wide range of hybrid device applications, such as medical imaging, self-energy-harvesting touch screens and invisible robotic devices.

从光声成像换能器到用于触觉应用的透明致动器^{1,2,3,4,5,6,7}的众多混合超声光学设备都非常需要透明压电材料。然而，同时实现高压电性和完美透明性具有挑战性，因为大多数高性能压电体都是包含高密度光散射畴壁的铁电体。在这里，通过相场模拟和实验相结合，我们展示了一种使用交流电场来设计原本不透明的菱面体 Pb(Mg _1/3 Nb _2/3 )O ₃ -的畴结构的相对简单的方法。 PbTiO ₃(PMN-PT) 晶体同时产生近乎完美的透明度、超高压电系数d ₃₃（大于 2,100 皮库仑/牛顿）、出色的机电耦合系数k ₃₃（约 94%）和大的电光系数γ ₃₃（约每伏220皮米），这远远超过了常用的透明铁电晶体LiNbO ₃的性能。我们发现增加畴尺寸会导致[001]取向的菱面体PMN-PT晶体的d ₃₃值更高，这挑战了减小畴尺寸总是导致更高压电性的传统观念^8,9,10。这项工作提出了通过铁电畴工程实现高透明度和压电性的范例，我们希望这里报道的透明铁电晶体能够为广泛的混合设备应用提供途径，例如医学成像、自能收集触摸屏和看不见的机器人设备。