Ultrahigh energy density dielectric film: Dielectrics help hold charge as capacitors and are fundamental energy storage components. Improving energy density and other properties may help these materials be more competitive with batteries for energy storage applications. Pan et al. introduced a specific type of nanodomain structure in a BiFeO ₃ -BaTiO ₃ -SrTiO ₃ solid solution that dramatically increased the energy density. The nanodomains were organized so as to minimize energy loss during polarization switching. The enhancement in the dielectric properties suggests that the strategy may be useful for designing high-performance dielectrics. Science , this issue p. 578

Samarium supersensors: Piezoelectric materials produce electric charge in response to changes in stress and are thus good sensor materials. One challenge has been growing single-crystal piezoelectrics with uniform properties. As of now, much of the crystal is discarded because of compositional variations. Li et al. synthesized single crystals of samarium-doped Pb(Mg _1/3 Nb _2/3 )O ₃ -PbTiO ₃ that have uniform and extremely high piezoelectric properties (see the Perspective by Hlinka). These crystals are ideal for a variety of sensing applications and could reduce cost by eliminating waste. Science , this issue p. 264 ; see also p. 228

Ferroelectrics are essential components in a wide range of applications, including ultrasonic transducers, sensors, and actuators. In the single crystal form, relaxor-PbTiO₃ (PT) piezoelectric materials have been extensively studied due to their ultrahigh piezoelectric and electromechanical properties. In this article, a perspective and future development of relaxor-PT crystals are given. Initially, various techniques for the growth of relaxor-PT crystals are reviewed, with crystals up to 100 mm in diameter and 200 mm in length being readily achievable using the Bridgman technique. Second, the characterizations of dielectric and electromechanical properties are surveyed. Boundary conditions, including temperature, electric field, and stress, are discussed in relation to device limitations. Third, the physical origins of the high piezoelectric properties and unique loss characteristics in relaxor-PT crystals are discussed with respect to their crystal structure, phase, engineered domain configuration, macrosymmetry, and domain size. Finally, relaxor-PT single crystals are reviewed with respect to specific applications and contrasted to conventional piezoelectric ceramics.