Frequency and temperature-dependence of dielectric permittivity and electric modulus studies of the solid solution Ca_0.85Er_0.1Ti_1−xCo_4x/3O₃ (0 ≤ <i>x</i> ≤ 0.1)

The dielectric properties of Ca_0.85Er_0.1Ti_1-<i>x</i> Co_4<i>x</i>/3O₃ (CETCo _<i>x</i> ) (<i>x</i> = 0.00, 0.05 and 0.10), prepared by a sol-gel method, were systematically characterized. The temperature and frequency dependence of the dielectric properties showed a major effect of the grain and grain boundary. The dielectric constant and dielectric loss of CETCo _<i>x</i> decreased sharply with increasing frequency. This is referred to as the Maxwell-Wagner type of polarization in accordance with Koop's theory. As a function of temperature, the dielectric loss and the real part of permittivity decreased with increasing frequency as well as Co rate. Indeed, a classical ferroelectric behavior was observed for <i>x</i> = 0.00. The non-ferroelectric state of the grain boundary and its correlation with structure, however, proved the existence of a relaxor behavior for <i>x</i> = 0.05 and 0.10. The complex electric modulus analysis <i>M*</i>(<i>ω</i>) confirmed that the relaxation process is thermally activated. The normalized imaginary part of the modulus indicated that the relaxation process is dominated by the short range movement of charge carriers.