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.