As the core component of high-precision positioning and force conversion systems, piezoelectric actuators play an irreplaceable role in precision manufacturing fields such as aerospace, automotive engineering, and biological sampling. With the continuous expansion of the global piezoelectric industry, the industry has put forward stringent requirements for actuators in terms of nanometer-scale displacement resolution, millisecond-level response speed, and high power density. Currently, lead-based relaxor ferroelectrics remain the mainstream choice for research and application in this field due to their excellent electromechanical properties, particularly their key role in micro-displacement compensation. However, existing high-performance piezoelectric materials often face complex external disturbances during actual service, which has become a bottleneck restricting the long-term stable operation of devices.

The main challenge currently facing piezoelectric materials is that soft relaxor ferroelectrics with optimal performance are highly susceptible to mechanical loading, alternating electric fields, and ambient temperature fluctuations. When actuators deliver actual mechanical work, high stress loads often lead to a nonlinear relationship between driving voltage and strain, and can even induce ferroelastic domain switching, resulting in significant performance degradation. Furthermore, how to balance a high piezoelectric coefficient with thermal stability over a wide temperature range, while reducing energy losses caused by constrained domain wall motion, remains an unresolved challenge in the field. To address these challenges, researchers are introducing local structural heterogeneity through approaches such as rare-earth ion doping, aiming to achieve high reliability and high energy efficiency in electromechanical conversion under extreme environments.

To address the above issues, a research team composed of Foshan Xianhu Laboratory, Wuhan University of Technology, City University of Hong Kong, and other institutions conducted systematic studies using ZEPTOOLS' ZEM series benchtop scanning electron microscope. By introducing 2.5% europium doping into PMN-PZ-PT relaxor ferroelectric ceramics, they successfully constructed a morphotropic phase boundary structure with highly mobile nanodomains and revealed the stress-dominated electromechanical behavior transition mechanism, providing key design criteria for developing piezoelectric actuators with both high output work density and extreme environmental thermal stability.

Title: Dynamic electromechanical behavior of Eu-doped PMN-PZ-PT ceramics: Stress dominance and thermal stability for actuator applications
Journal: Acta Materialia
URL: doi.org/10.1016/j.actamat

The research team prepared europium-doped lead magnesium niobate-lead zirconate titanate ternary piezoelectric ceramics via solid-state sintering. By systematically adjusting the lead titanate content, they successfully constructed a composition near the morphotropic phase boundary. Experimental results showed that at a lead titanate content of 0.33, the material exhibited excellent electromechanical properties, with a piezoelectric charge coefficient of 1030 pC/N and a piezoelectric strain coefficient as high as 1310 pm/V under a low electric field. This significant performance enhancement originates from the polarization rotation process induced by multiphase coexistence at the phase boundary, as well as the local structural heterogeneity caused by europium ion doping, effectively lowering the energy barrier for ferroelectric domain switching.

In exploring the physical origin of the high piezoelectric response, the ZEPTOOLS ZEM series benchtop scanning electron microscope played a key role. The researchers used the high-resolution imaging capability of this instrument to precisely observe the microstructural features of the ceramic fracture surface. The observations revealed a complex domain configuration inside the ceramic, containing randomly distributed macrodomains and nanodomains. This microstructure exhibits well-controlled switching characteristics under external electrical stimulation. The precise characterization by scanning electron microscopy demonstrated the existence of highly mobile domain walls within the material, providing direct experimental evidence for the contribution of reversible domain wall motion to electromechanical conversion efficiency.

To address the complex loads experienced by actuators during actual service, the researchers systematically evaluated the dynamic evolution of the ceramic under uniaxial prestress ranging from 0 to 100 MPa. The study found a significant transition from an electric-field-controlled mechanism to a stress-controlled mechanism. In the low prestress range below 20 MPa, mechanically assisted non-180° domain switching significantly enhanced polarization and strain output. However, when the prestress exceeded 20 MPa, a severe domain wall pinning effect began to inhibit domain motion, causing stress to replace the electric field as the key external factor dominating the electromechanical response. This reveals the difference in output characteristics of actuators under various loading conditions.

To verify the reliability of the ceramic in precision positioning systems, the team conducted an in-depth study of the mechanical work density and thermal stability under coupled temperature and stress. The material achieved a high mechanical work density of 0.040 J/cm³ under a prestress of 40 MPa, with an electromechanical conversion efficiency of 46.4%. More critically, in wide-temperature-range tests from 30 to 120 °C, the fluctuation in mechanical energy output remained within 20%, demonstrating that the stress-controlled mechanism can effectively mitigate temperature-induced phase transition fluctuations. This finding provides important theoretical support and data reference for the design of next-generation multilayer piezoelectric actuators with high durability and energy efficiency.

The ZEPTOOLS ZEM series scanning electron microscope is a highly integrated, portable, and cost-effective scientific research instrument. It features fast pump-down, high imaging speed, and a variety of signal detector options, making it suitable for morphological observation and compositional analysis, as well as adapting to various in-situ experimental needs. The instrument has low requirements for the installation environment, is not sensitive to floor level, and is easy to operate, allowing non-specialists to quickly become proficient. It can be widely applied in fields such as new materials development, life sciences, failure analysis, industrial quality inspection, and more, providing a powerful and cost-effective high-performance microscopic characterization solution for research institutions and industrial users.