Ultrahigh Piezoelectric Performance through Synergistic Compositional and Microstructural Engineering

Piezoelectric materials enable the conversion of mechanical energy into electrical energy and vice-versa. Ultrahigh piezoelectricity has been only observed in single crystals. Realization of piezoelectric ceramics with longitudinal piezoelectric constant (d₃₃ ) close to 2000 pC N^-1 , which combines single crystal-like high properties and ceramic-like cost effectiveness, large-scale manufacturing, and machinability will be a milestone in advancement of piezoelectric ceramic materials. Here, guided by phenomenological models and phase-field simulations that provide conditions for flattening the energy landscape of polarization, a synergistic design strategy is demonstrated that exploits compositionally driven local structural heterogeneity and microstructural grain orientation/texturing to provide record piezoelectricity in ceramics. This strategy is demonstrated on [001]_PC -textured and Eu³⁺ -doped Pb(Mg_1/3 Nb_2/3 )O₃ -PbTiO₃ (PMN-PT) ceramics that exhibit the highest piezoelectric coefficient (small-signal d₃₃ of up to 1950 pC N^-1 and large-signal d₃₃ * of ≈2100 pm V^-1 ) among all the reported piezoelectric ceramics. Extensive characterization conducted using high-resolution microscopy and diffraction techniques in conjunction with the computational models reveals the underlying mechanisms governing the piezoelectric performance. Further, the impact of losses on the electromechanical coupling is identified, which plays major role in suppressing the percentage of piezoelectricity enhancement, and the fundamental understanding of loss in this study sheds light on further enhancement of piezoelectricity. These results on cost-effective and record performance piezoelectric ceramics will launch a new generation of piezoelectric applications.

Synthesis, Giant Dielectric, and Pyroelectric Response of [001]-Oriented Pr3+ Doped Pb(Mg1/3Nb2/3)O₃-PbTiO₃ Ferroelectric Nano-Films Grown on Si Substrates

The [001]-oriented Pr³⁺ doped Pb(Mg_1/3Nb_2/3)O₃-0.30PbTiO₃ (Pr-PMN-PT) thin films with a composition near the morphotropic phase boundary (MPB) were synthesized by a sol–gel method. The crystal structure was characterized using X-ray diffraction. It was found that a single perovskite phase was achieved in Pr-PMN-PT thin films annealed at 650 °C for 3 min. The dielectric constant (ε_r) value was 2400 in 2.5% Pr-PMN-PT thin films at room temperature, 110% higher than that of pure PMN-PT samples. Through 2.5% Pr³⁺ doping, remanent polarization (P_r) and coercive field (E_c) values increased from 11.5 μC/cm² and 35 kV/cm to 17.3 μC/cm² and 63.5 kV/cm, respectively, in PMN-PT thin films. The leakage current densities of pure and 2.5% Pr-PMN-PT thin films were on the order of 1.24 × 10⁻⁴ A/cm² and 5.8 × 10⁻⁵ A/cm², respectively, at 100 kV/cm. A high pyroelectric coefficient (p_y) with a value of 167 μC/m²K was obtained in 2.5% Pr-PMN-PT thin films on Si substrate, which makes this material suitable for application in infrared detectors.

Monoclinic MA domains in anisotropically strained ferroelectric K0.75Na0.25NbO3 films on (110) TbScO3 grown by MOCVD

A highly regular one-dimensional domain pattern is formed in ferroelectric K0.75Na0.25NbO3 thin films grown on (110) TbScO3 substrates using metal–organic chemical vapour deposition (MOCVD). The domain pattern exhibits a lateral periodicity of about 50 nm and extends over several micrometres. The monoclinic symmetry of the domains is controlled by the elastic anisotropy of K0.75Na0.25NbO3 and the anisotropic lattice strain, which is highly compressive in one in-plane direction and weakly tensile in the corresponding orthogonal direction. Using piezoresponse force microscopy and X-ray diffraction, the monoclinic MA phase is identified, which is associated with both a strong vertical and a lateral electric polarization component. The lateral component of the polarization vector is collinear with the ±[{\overline 1}10]pc shear direction of the pseudocubic unit cell of the film and changes periodically by 180° in adjacent domains. A structural variant of a 90° rotated MA domain pattern, where the monoclinic distortion of the pseudocubic unit cells occurs along ±[110]pc, is also observed. However, this variant appears with significantly lower probability, in agreement with energy considerations based on linear elasticity theory. Thus, the incorporation of highly anisotropic lattice strain provides the opportunity to grow one-dimensional nanostructures with high ferroelectric properties.

Temperature and electric field induced phase transition in [110]C-oriented 0.63Pb(Mg1/3Nb2/3)O3–0.37PbTiO3 single crystals

Temperature-dependent domain configurations were studied for both unpoled and poled [110]_C-oriented 0.63Pb(Mg_1/3Nb_2/3)O₃–0.37PbTiO₃ (PMN–0.37PT) single crystals by polarized light microscopy (PLM).