Microstructure, electrical and optical properties of NBT–xBZT lead-free single crystals

Lead-free single crystals (100-x)Na0.5Bi0.5TiO3-xBi(Zn0.5Ti0.5)O3 (x = 0, 8, 20, 30) were grown by the top seeded solution growth (TSSG) method. With the addition of Bi(Zn0.5Ti0.5)O3 (BZT), the NBT-xBZT crystals change from rhombohedral to tetragonal and the NBT-8BZT lead-free single crystals are near the morphotropic phase boundary (MPB) by studying the phase structures via X-ray powder diffraction (XRPD) and the domain structures via polarizing microscope (PLM). And with the addition of BZT, the electrical performances of NBT-xBZT crystals exhibit a trend of increasing firstly and then decreasing, in which the maximum values of piezoelectric constant d33 can be found in NBT-8BZT crystals, being 127 pC/N. The improvements of electrical performance can be attributed to the coexistence of rhombohedral and tetragonal near MPB with more possible crystallographic orientations, inducing crystals can be poled more easily, which can be verified by the piezo-response force microscopy (PFM). Furthermore, the trend of optical properties is similar to the electrical properties, in which the maximum optical transmittance is as much as 90%.