Decrease in dielectric loss of CaCu3Ti4O12 by the addition of TeO2

CaCu3Ti4O12 (CCTO) has challenged for the last few years the scientific community due to its large dielectric constant, which is almost temperature and frequency independent, from 100 K to 400 K and from 1 kHz to 1 MHz, respectively. This makes the material desirable for many electronic applications. However, the dissipation factor is very large, with tan delta values, at room temperature and 1 kHz, higher than 0.1. In our work we report how the addition of TeO2 lowers the dielectric loss and, although there is a decrease of dielectric constant of doped samples relatively to the undoped one, high dielectric constant values are still being reached. The sample of doped CCTO with 1.5% of TeO2 by weight, presents, at room temperature and 60 kHz, a large dielectric constant, over 3000, and a dissipation factor around 0.09, which represents a decrease on tan delta over 30% relatively to the CCTO undoped sample. Two relaxation processes were identified for all the samples, one at MHz region and the other one at low frequency region (<1 kHz). DC bias voltage was applied up to 40 V and a strong dc bias influence on the low frequency region was observed both at dielectric and impedance responses of the undoped sample, which was much weaker than the dc bias effects on the 4% Te doped sample. Dielectric measurements will be discussed and correlated with the samples' microstructure, supported on internal barrier layer capacitance (IBLC) and surface barrier layer capacitance (SBLC) models. (C) 2010 Elsevier B.V. All rights reserved.