Crystal Structure, dielectric and ferroelectric properties of (Bi0.5Na0.5)TiO3–(Ba,Sr)TiO3 lead-free piezoelectric ceramics

The crystal structure, microstructure, dielectric and ferroelectric properties of (1 − x)(Bi0.5Na0.5)TiO3–x(Ba0.7Sr0.3)TiO3 (BNBST30-x, x = 0–0.12) lead-free piezoelectric ceramics were studied in this work. Structural variation according to (BNBST30-x) composition was carefully investigated by X-ray diffraction analyses. A rhombohedral–tetragonal morphotropic phase boundary (MPB) is found at BNBST30-8 composition which shows the highest remanent polarization value. Smallest coercive field value is observed at the tetragonal-side of MPB, i.e. BNBST30-10, instead of MPB composition. The addition of Sr2+ ions plays a role as soft dopant on the dielectric properties in the present BNBST systems. In comparison with the MPB compositions containing various Sr2+ ratios, the dielectric and piezoelectric properties (ɛ33T/e0 and d33) are effectively enhanced when Sr2+ ratio is higher. Besides, Sr2+ allows to enlarge the cell volume that is also advantageous for the improvement of dielectric and piezoelectric performances.