Fig. 4. (a, b) Temperature-dependence at 100 kHz, and (c, d) frequency-dependent at room temperature of dielectric permittivity (a, c) and dielectric loss (b, d) of BNKT-1075 to 1100.Figure optionsDownload full-size imageDownload as PowerPoint slide
In Fig. 4(c) it BX-795 is shown that at low frequencies, permittivity increases drastically, when frequency decreases, as a consequence of polarization between grains characteristic of the polycrystalline materials. Additionally, from Fig. 4c and d a relaxation process at high frequency (~8 MHz), which is associated with a dipolar relaxation phenomena can be observed. In these samples, the improvement in the real permittivity value with the sintering temperature could be related to the secondary phase formation, the grain size increase and the densification degree.
In order to observe the temperature and frequency dependence, Fig. 5 shows the relative permittivity as a function of temperature of sample BNKT-1100, at various frequencies. The shift in the maximum temperature depending on frequency and the diffusive phase transition for all samples suggest the relaxor-like behavior of vascular plants ceramics. The broadening of the real premittivity peak around the dielectric maximum temperature may be due to compositional fluctuations occurring at A- and B-sites of the perovskite unit cell, as a result of the secondary phase formation.