Investigation of the crystal-oriented behavior of rare earth substituted Sr₂NaNb₅O₁₅ lead-free piezoelectric materials under a high magnetic field

The crystal-orientation behavior of Sr2NaNb5O15 (SNN) lead-free piezoelectric materials under a magnetic field was investigated by substituting rare-Earth elements (Ln = Nd, Eu, Ho, Yb), which were selected based on their ionic radii and magnetic or non-magnetic ions. The magnetic ions, Nd, Ho, and Yb, did not affect the magnetic anisotropy of the SNN. The nonmagnetic ions (Eu3+) changed from the a, b-axis orientation to the c-axis orientation in the direction of the magnetic field. The Eu-substituted SNN powders revealed that the degree of orientation of the c-axis increased as the Eu content increased. Consequently, c-axis-oriented Eu-substituted SNN ceramics were obtained with the degree of orientation of 0.9. The diamagnetism along the a, b-axis became larger than that along the c-axis owing to a decrease in the c-axis lattice constant. By substituting Eu with SNN, the piezoelectric properties decreased as the hardening of SNN progressed.