Dielectric relaxation on Ba_(1-x)Bi_(2x/3)Zr_(0.25)Ti_(0.75)O_3 ceramic

摘要

Polycrystalline (Ba_(1-x)Bi_(2x/3)Zr_(0.25)Ti_(0.75)O_3) (x=0.025) (BBZT) ceramic, is prepared by solid-state reactioa The X-ray diffraction of the sample at room temperature shows single-phase compound in a cubic crystal system. The electrical behavior (complex impedance Z*, complex permittivity ε*, complex modulus M*) of the BBZT ceramic has been studied by non-destructive complex impedance spectroscopy (CIS) as a function of frequency at different temperatures. Grain and grain boundary conduction is observed from complex impedance spectrum by the appearance of two semicircular arcs in the Nyquist plot. The presence of non-Debye type multiple relaxations has been confirmed by complex modulus analysis. The Nyquist plot shows the negative temperature coefficient of resistance (NTCR) character of BBZT. Variation of ac conductivity as a function of frequency shows that the compound exhibits Arrhenius-type of electrical conductivity. The ac conductivity data are used to evaluate the density of states at Fermi level and activation energy of this ceramic. The dc electrical and thermal conductivities of grain and grain boundary have been discussed.