Dielectric, electromechanical coupling properties of Mn-doped Na0.5Bi0.5TiO3–BaTiO3 lead-free single crystal

Mn-doped 0.948Na0.5Bi0.5TiO3–0.052BaTiO3 (NBBT94.8/5.2) lead-free single crystal with excellent piezoelectric and electromechanical coupling properties was successfully grown by top-seeded solution growth method (TSSG). X-ray powder diffraction measurement showed that the as-grown crystal possesses rhombohedral perovskite structure. The Mn-doped NBBT94.8/5.2 single crystal exhibits apparent diffused dielectric behavior, in which the diffusiveness index α is 1.99 for the [001]-oriented crystal planes. A notable thermal hysteresis is disclosed for the rhombohedral-tetragonal phase transition between heating and cooling studies in the dielectric property. The electromechanical coupling coefficients of Mn-doped NBBT94.8/5.2 were determined experimentally using the resonance–antiresonance technique. The room-temperature electromechanical coupling coefficients k 31, k 31〈110〉, k 33, k t are 35.9%, 35.5%, 68.5%, 58.7%, respectively. The room-temperature piezoelectric constants d 33, d 31 reach as high as 457, 138 pC/N respectively. The value of k t increases slightly with the increase of temperature from −80 to 70°C, demonstrating a relatively stable thermal electromechanical coupling property.