摘要
The polycrystalline samples of complex tungsten bronze(TB)Na_(2)Pb_(2)R_(2)W_(2)Ti_(4)V_(4)O_(30)(R=Dy,Pr)compounds were prepared by solid-state reaction technique.Room-temperature preliminary structural studies confirm the formation of the compounds in the orthorhombic crystal system.Detailed studies of electrical properties of the materials using complex impedance spectroscopy technique exhibit that the impedance and related parameters are strongly dependent upon temperature and microstructure(bulk,grain boundary,etc).An observation of negative temperature coefficient of resistance(NTCR)suggests the materials have semiconducting properties.The variation of AC conductivity with temperature shows a typical Arrhenius behavior of the materials.Both the samples obey Jonscher’s universal power law.The existence of hopping mechanism in the electrical transport processes in the system with non-exponential type of conductivity relaxation is confirmed by electrical modulus analysis.
