Phase transitional behavior and dielectric properties of lead free (1-x)(K0.5Na0.5)NbO3-xBi(Zn0.5Ti0.5)O3 ceramics

Lead-free ceramics based on potassium sodium niobate [(K0.5Na0.5)NbO3; KNN]-bismuth zinc titanate [Bi(Zn0.5Ti0.5)O3; BZT] were prepared by the modified-conventional mixed oxide route with normal sintering. The crystal structure and ferroelectric phase transitions were studied by means of X-ray diffraction, thermal and dielectric measurements. The ceramics with perovskite structure were in orthorhombic phase at x ≤ 0.010. When reaching 0.01 < x ≤ 0.03, they became a rhombohedral perovskite structure; and with increasing BZT content, cubic within the studied composition range. The phase Bi2Ti2O7 with cubic structure began to appear at x > 0.25 and became dominant while increasing the content of BZT. Furthermore, the phase transition temperature of orthorhombic-tetragonal (TO-T) and tetragonal-cubic (TC) decreased when a small amount of BZT was added. As the amount of BZT concentration increased, the structure became denser, and well developed grain morphology with almost no porosity was finally obtained.