Nb2O5-based oxide ceramics and single crystals-investigation of dielectric properties

The behavior of enhancements of dielectric constant of Nb2O5 through small substituents of TiO2 is of interest. The ceramics of these solid solutions were prepared by the conventional mixed oxide method. Single crystal fibers were grown by the Laser-Heated Pedestal Growth (LHPG) technique, which is considered to be a powerful tool for rapid growth of high-melting temperature oxides and incongruent melting compositions. The dielectric properties as function of temperature (−180 to 180 °C) and frequency (1 kHz to 1 MHz) were measured. The direct-current (dc) electric field dependence of the dielectric constant was also studied. The results show that a strong dielectric dispersion exists in a large frequency range, which implies that the relaxation process involved is not of a Debye-type. Relaxation dispersion was estimated by examining the influence of the cluster size distribution. The modified Devenshire relation including a cluster term was used to analyze data of dc bias field dependence of the dielectric constant, which gives the fitted parameters corresponding to cluster size distribution and their polar cluster polarization.