Diversiform electrical and thermal expansion properties of (1 − x)Ba0.95Ca0.05Ti0.94Zr0.06O3–(x)Dy lead-free piezoelectric ceramics influenced by defect complexes

(1 − x)Ba0.95Ca0.05Ti0.94Zr0.06O3–(x)Dy (x = 0–0.90 mol%) lead-free ceramics were prepared at 1190 °C with as-synthesized nanoparticles via a modified Pechini polymeric precursor method. X-ray powder diffraction, Raman spectrometer, and X-ray photoelectron spectroscopy were used to investigate the phase, symmetry, and valence state, respectively. The results indicated dysprosium could induce the phase transformation from O to R. The mechanism of defect complexes and oxygen vacancies that influenced by various dysprosium contents were discussed in detail. The results of dielectric, ferroelectric, and piezoelectric characteristics suggested the electrical properties were initially elevated with a trifling addition of dysprosium contents, and then decreased with further increased x. Moreover, reasons for diversified electrical properties, i.e., imbalanced long-range and short-range forces, changed octahedron structure, defect dipole, pinching effects of domain wall and element electronegative, were all stated in detail. The optimal physical properties, d33 = 371 pC/N, Qm = 87, and CTE2 = 1.23 × 10−5 K−1, were detected at x = 0.60 mol%, and those findings were regarded as prospect in the development of lead-free ferroelectric ceramic materials.