Chemical interpretation, enhanced ferroelectric property and dielectric breakdown strength of CuO-added Sr₂Nb₂O₇ ceramics

The structural interpretation and electrical properties of perovskite layer structured (PLS) Sr₂Nb₂O₇-xwt%CuO ceramics prepared by solid-state reaction method are investigated. The chemical interpretation of enhanced piezoelectricity is confirmed to be attributed to the rotation and/or distortion of oxygen octahedron caused by possible Cu²⁺ substitution at the A-site of Sr₂Nb₂O₇ by XRD refinement and variable-temperature Raman spectra. Sr₂Nb₂O₇-xwt%CuO (x = 0.3, 0.5 and 0.7) ceramics shows enhanced ferroelectric properties with a larger P_r of ∼4.1 μC/cm² and a smaller E_c of ∼63.1 kV/cm. This study further explains the cations in A-site play a major structural role in the polarization process for PLS system. It was found that dielectric breakdown strength increases up to 258.8 kV/cm and then decreases gradually with the increase of CuO content. Impedance spectroscopy indicated that CuO addition could be helpful in increasing the grain boundary resistance then dielectric breakdown strength.