Effects of Er3+–doping on dielectric and piezoelectric properties of 0.5Ba0.9Ca0.1TiO3–0.5BaTi0.88Zr0.12O3–0.12%La–xEr lead–free ceramics

0.5Ba0.9Ca0.1TiO3–0.5BaTi0.88Zr0.12O3–0.12%La–xEr (x = 0–0.5%) lead–free ceramics were prepared by a modified Pechini polymeric precursor method, and the effects of erbium contents (x) on the crystal structure, dielectric and piezoelectric properties were investigated. The samples showed high densification (relative density: ∼96.6%) with fine grain size (∼0.652 μm) under the synthesis conditions at x = 0.2%. The Curie temperature (TC) shifted toward lower temperature and orthorhombic–to–tetragonal phase transition temperature (TO–T) shifted toward higher temperature with addition of x, which was beneficial for elevating piezoelectric properties as pinched effect of the temperature. The diffuseness of the ceramics was receded with a small addition of x, because of disappeared oxygen vacancy and small area of polar nano–regions (PNRs) in the structure. The elevated piezoelectric constant (d33; ∼200 pC/N) and receded mechanical quality factor (Qm; ∼70) at x = 0.2% showed "softening effect" by donor doping. However, erbium showed "hardening effect" by accepter doping with the substitution of B sites in the matrix of ABO3 structure with excessive erbium contents.