Dielectric and piezoelectric properties of (K_(0.5)Na_(0.5))NbO_3-Ba(Zr_(0.05)Ti_(0.95)O_3 lead-free ceramics

摘要

Lead-free ceramics (1-x)(K_(0.5)Na_(0.5))NbO_3-xBa(Zr_(0.05)Ti_(0.95))O_3 doped with 1 mol % MnO_2 have been fabricated by pressureless sintering. With the MnO_2 doping, all the ceramics can be well sintered at 1100-1160 ℃ and exhibit a dense and pure perovskite structure. After the addition of Ba(Zr_(0.05)Ti_(0.95))O_3, a relax behavior is induced and both the cubic-tetragonal and tetragonal-orthorhombic phase transitions shift to lower temperatures. Coexistence of the orthorhombic and tetragonal phases is hence formed in the ceramics with 0.04 < x < 0.07 at room temperature. It is suggested that owing to the more possible polarization states resulting from the coexistence of the two phases, the piezoelectric and dielectric properties of the ceramics are enhanced significantly. The ceramic with x=0.06 exhibits the following optimum properties: d_(33)=234 pC/N, k_p=0.49, k_t=0.48, ε_r=1191, tan δ=1.20%, and T_c=318 ℃.