Cu-doping effect on dielectric properties of organic gel synthesized Ba4YMn3−xCuxO11.5±δ

Copper doped-Ba4YMn3−xCuxO11.5±δ samples were synthesized by an organic gel assisted citrate process. X-ray diffraction of compositions with x=0.002, 0.005, 0.01, 0.02 and 0.04 does not reveal any change of hexagonal perovskite structure on doping. The effects of Cu-doping on the microstructure and dielectric properties were investigated. Cu doping modifies the electrical properties at the level of the impedance characteristics of both grain and grain boundary and to understand these different behaviours, we have carried out high-resolution transmission electron microscopy analysis. Among the Ba4YMn3−xCuxO11.5±δ specimens studied, the composition x=0.002 shows a permittivity (ε′r) higher than the undoped compound and a lower loss tangent (tanδ) over several orders of magnitude of frequency. - Graphical abstract: Highlighting of many stacking faults (intergrowths) in substituted compounds with x>0.01 (right picture), which could explain the different dielectric properties observed in these compounds. However compounds with x>0.01 remain with a better stacking sequence as we can see on the left picture. Display Omitted - Highlights: • High permittivity of the Ba4YMn3−xCuxO11.5±δ. • Substitution leads to a mixed oxidation state for manganese: Mn4+/Mn3+. • Creation of oxygen vacancies which are responsible for stacking faults. • Highlighting relationship between Cu substitution and dielectric properties