Dielectric and piezoelectric properties of lead-free (Na0.5K0.5)NbO3–SrTiO3 ceramics

In this article, we report successful preparation of dense [(Na0.5K0.5)1−xSrx](Nb1−xTix)O3 (x=0.005–0.100) ceramics by ordinary sintering in air. The dependence of phase structure on doping content of SrO and TiO2 has been determined by the X-ray diffraction technique. It was found that the crystal structure changed from orthorhombic to tetragonal at x≈0.040. Dielectric study revealed that the dielectric relaxor behavior was induced by doping of SrO and TiO2 into (Na0.5K0.5)NbO3. The samples in the composition range from x=0.005 to 0.020 exhibited excellent electrical properties, piezoelectric constant of d33=90–96 pC/N, electromechanical planar and thickness coupling coefficients of kp=26.6–32.5% and kt=39.8–43.8%. The results show that the [(Na0.5K0.5)1−xSrx](Nb1−xTix)O3 ceramics are one of the promising lead-free materials for electromechanical transducer applications.