Some Optical, Electrical Properties of Lead Free KNN-CZN Ceramics

Lead free (1−x)K0.5Na0.5NbO3-xCa(Zn1/3Nb2/3)O3 (abbreviated KNN-xCZN) ferroelectric ceramics, with x = 0, 0.02, 0.04, 0.06, 0.08, 0.10, have been fabricated by the conventional solid-state reaction method. The effects of CZN content on the structure, microstructure and some optical, electrical properties of KNN-xCZN ceramics were studied in detail. The experimental results showed that the crystal structure of ceramics gradually transformed from orthorhombic phase into pseudo-cubic phase with doping of xCa(Zn1/3Nb2/3)O3. With increasing of the CZN concentration, the ceramic density increased and reached the highest value (4.29 g/cm3) at x = 0.08 mol, besides, the grain size of the ceramics decreased gradually, the microstructure more uniform, the grains are packed with clear grain boundaries, fewer pores, especially at x = 0.08 mol. With the dense and fine-grained microstructures, the optical transmission of the ceramics is strong, the ceramic sample with x = 0.08 mol exhibits stably high transmittance above 60% in the visible spectrum and the largest optical band gap energy (Eg = 3.0 eV) was obtained. The Curie temperature (TC) decreases when the concentration of CZN increases. The broadness of dielectric peaks around Tm indicated a diffusive phase transition for all compositions suggesting the relaxor-like behavior of KNN-xCZN ceramic systems.

Electrical Properties of CuO-Doped PZT-PZN-PMnN Piezoelectric Ceramics Sintered at Low Temperature

The 0.8Pb(Zr0.48Ti0.52)O3-0.125Pb(Zn1/3Nb2/3)O3-0.075Pb(Mn1/3Nb2/3)O3 (PZT-PZN-PMnN) + x wt% CuO piezoelectric ceramics, where x = 0.0, 0.05, 0.075, 0.10, 0.125, 0.150, and 0.175, have been fabricated by the conventional solid-state reaction method and the B-site Oxide mixing technique (BO). The effect of CuO on the sinterability, structure, and electrical properties of PZT-PZN-PMnN ceramics was systematically studied. The CuO addition significantly reduced the sintering temperature of the ceramics from 1150°C to 850°C. Experimental results showed that with the doping of CuO, all the ceramics could be well sintered and exhibit a dense, pure perovskite structure. The specimen containing 0.125 wt% CuO sintered at 850°C showed the good electrical properties: the density of 7.91 g/cm3;the electromechanical coupling factor, kp = 0.55 and kt = 0.46;the dielectric constant, ε = 1179;the dielectric loss (tand) of 0.006;the mechanical quality factor (Qm) of 1174;the piezoelectric constant (d31) of 112 pC/N.

Structure and Electrical Properties of Fe₂O₃-Doped PZT-PZN-PMnN Ceramics

The 0.8Pb(Zr0.48Ti0.52)O3 – 0.125Pb(Zn1/3Nb2/3)O3 – 0.075Pb(Mn1/3Nb2/3)O3 + x wt% Fe2O3 ceramics (PZT-PZN-PMnN), where x = 0 ÷?0.35, has been prepared by two-stage calcination method. The effect of Fe2O3 content on the crystal structure and electrical properties of ceramics has been investigated. The results of X-ray diffraction (XRD) show that all samples have pure perovskite phase with tetragonal structure, the c/a ratio increases with increasing Fe2O3 content. At x = 0.25, electrical properties of ceramics are best: the density (r) of 7.86 g/cm3, the electromechanical coupling factor (kp) of 0.64, the dielectric constant (εr) of 1400, the dielectric loss (tand) of 0.003, the mechanical quality factor (Qm) of 1450, the piezoelectric constant (d31) of 155 pC/N, and the remanent polarization (Pr) of 37 μC/cm2, which makes it as a promising material for high power piezoelectric devices.