Shear piezoelectric properties d24 and k24 of a [001] poled KNNTL-Mn single crystal

Abstract

The distributions of d₂₄ and k₂₄ in the 3D space of a [001] poled (K, Na, Li)(Na, Ta)O₃:Mn (KNNTL-Mn) single crystal were investigated by the coordinate system rotation method. For the [001] poled KNNTL-Mn single crystal, the maximum piezoelectric strain constant d₂₄ was 607.4 pC N⁻¹, which was 9.2 times larger than the value in the original coordinate system and higher than d₃₃. The maximum electromechanical coupling coefficient k₂₄ was 0.83, which was 2.7 times larger than the original one. It was found that d₂₄ and d₁₅ as well as k₂₄ and k₁₅ were only equal in the Z-axis direction. In the other directions, d₂₄ and k₂₄ were greater than d₁₅ and k₁₅, respectively. In addition, compared with the 24-shear modes of other four lead-free single crystals (KNN, KNNT, KNNTL, and NBBT95/5) and the PZT-5H piezoelectric ceramics, the 24-shear mode of the KNNTL-Mn single crystals was found to be optimal in the lead-free single crystals. Although the maximum d₂₄ of the KNNTL-Mn single crystal was slightly smaller than that of the PZT-5H piezoelectric ceramics, it was lead-free and had a larger electromechanical coupling coefficient, k₂₄, and a higher Curie temperature than the PZT-5H piezoelectric ceramics. The [001] poled KNNTL-Mn single crystal is expected to be used in 24-shear mode piezoelectric sensors for non-destructive testing and structural health monitoring.