By introducing trace amounts of the element samarium (Sm), researchers greatly enhanced the performance of piezoelectric crystals used in advanced piezoelectric devices like sensors, a new study reports. While amounts of the rare-earth element are relatively miniscule - about one atom per thousand atoms of the parent crystal - its effect on the piezoelectric properties of the materials is profound, nearly doubling their performance, the results show. Under mechanical stress, piezoelectric materials generate an electric charge, which makes them ideally suited for use in devices such as underwater sonars and medical imaging systems. The most advanced piezoelectric devices often use a perovskite oxide crystal known as PMN-PT, which far outperforms other common piezoelectric materials. However, despite the ever-growing demand for more advanced piezoelectric devices, progress towards improving the performance of PMN-PT crystals has been slow and limited by the long-standing challenge of growing single crystal piezoelectric with uniform properties, according to the authors. Fei Li and colleagues report on a new strategy for synthesizing single-crystals of Sm-doped PMN-PT, which have exceptionally high uniformity and piezoelectric properties. While as-grown PMN-PT crystals already possess high piezoelectric coefficients (the amount of charge generated for each unit of force) that range from 1200-2500 picocoulombs per newton, the coefficients generated from Li et al.'s Sm-doped crystals are nearly double - measuring 3400-4100 picocoulombs per newton. Further analysis of the material revealed that the "giant" piezoelectric properties of the Sm-doped crystals arise from the enhanced structural heterogeneity within the crystal, which suggests that rare-earth doping circumvents the issue of non-uniform crystals. The larger size crystals afforded by the new method could reduce costs and material waste and provide new commercialization opportunities for high-performance applications. In a related Perspective, Ji?í Hlinka discusses the study's results in more detail.
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Journal
Science