Study on electric modulus, complex modulus and conductivity properties of Nb/Sm, Gd doped barium titanate-lithium ferrite ceramic composites

Abstract

The (90)BaTi(1−2x) YxNbxO3 + (10)Li0.5Fe2.5O4 (Y = Gd, Sm and x = 0, 0.05, 0.1) composites are prepared using the solid state method. The structural properties like X-ray diffraction (XRD), FESEM, electrical properties like electric modulus (M′), complex electric modulus (M″) and conductivity properties of doped and undoped composites have been discussed. The XRD studies confirm the tetragonal structure of all composites. FESEM studies reveal an increase in the average grain size of the (90)BaTiO3 + (10)Li0.5Fe2.5O4 composite upon doping with Gd/Nb and Sm/Nb. As and when the temperature of the sample is decreased, with frequency is similar but its conductivity has decreased. In the high frequency region, the frequencies beyond 100 MHz, the conductivity of all composites are not zero, which shows the existence of hopping of electrons to a new site. The real electric modulus (M′) of composites confirm the occurrence of dispersion in all composites at all temperatures. The imaginary electric modulus (M″) increases with frequency and exhibits a peak at a certain frequency. The relaxation time of all composites reveals the short range movement of charge carriers. The nearly same value of activation energy of all composites reveals that the distribution of energy barriers in the Gd/Nb and Sm/Nb doped 0.9BT0.1LF composites. The area of semicircles of all composites increase and the shift of the intercept of a semicircle towards the higher value of M′ represents an increase in the capacitance. The normalized scaling behavior of all composites is studied by plotting normalized parameters M″/M″maxVs Log (f/fmax).