Effect of copper on the structural, morphological and dielectric properties of Pb1−xCuxNb2O6 (x = 0, 1/3, 1/2, 2/3 and 1) perovskites

Tungsten bronze structure-based PbNb2O6 ceramics are functional materials and are usually known as low-density ceramics. The low-density property may limit their practical applications. In this study, Cu-substituted PbNb2O6, with different concentrations, was prepared by a well-known solgel auto-combustion method. X-ray diffraction analysis confirmed the formation of rhombohedral perovskite phase for PbNb2O6 which is transformed to monoclinic phase upon complete replacement of Pb by Cu. The surface morphology of all the samples suggested that, with the increase in copper content, the grain size decreased, which resulted in an increase in the density of these ceramics. Energy-dispersive X-ray spectroscopy assured the presence of all the elements in the samples in accordance with their empirical formulae. Fourier transform infrared spectroscopy confirmed complete combustion, and the downward peaks in the corresponding spectra were purely related to perovskites. Frequency-dependent dielectric analysis showed that the dielectric constant and conductivity of PbNb2O6 improved with increasing Cu contents and less than 1% dielectric loss was achieved. In addition, complex impedance spectroscopy and complex modulus analysis revealed the existence of non-Debye-type relaxation in these compositions.