High frequency studies on dielectric, impedance and Nyquist properties of BaTiO3–Li0.5Fe2.5O4 composite ceramics substituted with Sm and Nb for microwave device applications

Abstract

The BaTiO3–Li0.5Fe2.5O4 composite ceramics doped with Sm and Nb having chemical formulae (90)BaTi(1−2x)NbxSmxO3+(10)Li0.5Fe2.5O4 (x = 0, 0.05 and 0.1) were prepared using solid state reaction technique. The structural, qualitative structural information regarding functional groups, dielectric, Nyquist plots, the variation of impedance with frequency (1–10 MHz) at different temperatures, the variation of dielectric properties, A.C. conductivity and impedance with frequency between 1 MHz and 3.2 GHz at 30 °C of composites are investigated. The X-Ray diffraction peaks indicate the formation of tetragonal structure of all composites with a small amount of ferrite phase. From fourier transform infrared spectroscopy (FTIR) measurements, the presence of function groups have been identified. The dielectric studies reveal the higher value of the dielectric constant of all composites at low frequency regime due to an interfacial polarization. The dielectric constant of BTNS0.1 is higher than BTLF, BTNS0.05 which shows dispersion at low frequency region. The dielectric loss of BTLF decreases in the frequency region 80MHz–1.10 GHz. The impedance (Z′) of all composites decreases with an increase in the frequency and temperature. The impedance studies show the complex behaviour of all the composites which indicates the enhancement of AC conductivity of material at higher frequencies beyond 3 GHz. The conductivity studies of composites show dispersion characteristics among the samples and the conductivity of composites is enhanced by incorporation of Nb, Sm in BTLF composites. The radii of all semi circles decrease with increase in temperature which represents conductivity of composites increases with increase in temperature.