Influence of calcium doping on microstructure, dielectric and electric properties of BaBi2Nb2O9 ceramics

Abstract

Barium bismuth niobiate (BaBi 2 Nb 2 O 9) ceramics modified by calcium were prepared by solid state synthesis and two-step sintering process. An impact of calcium substitution on the A site of perovskite block is presented. The investigations are focused on dielectric as well as electric aspects of the modification. The presented results reveal that the concentration of a space charge is not preserved, what is surprising due to the homovalent nature of the dopant and no reason for creating additional lattice defects and charges connected. However, not only the valence of ions, but also the calcium-oxygen and barium-oxygen bond strength should be taken into consideration. Since the calcium-oxygen bond is probably weaker the loss of the bismuth oxide is expected to increase with an increase in the calcium content. Such a scenario results in appearance of a large number of negative charge carriers connected with unsaturated oxygen ions.

The Effect of Pr Doping Contents on the Structural, Microstructure and Dielectric Properties of BaBi2Nb2O9 Aurivillius Ceramics

“…For the highest amount of modifier, the γ achieved smaller values; however, it never returns to its original value for pure BBN ceramics. The same upward trend in the parameter g was also observed in the case of simultaneous doping of BBN ceramics with Cu and Ta [33] ions [34]. This allows us to speculate that the praseodymium ions, in contrast to vanadium ones [35], enhance the disorder of the crystal lattice [30], which should also influence the frequency dispersion observed in the BBN ceramics.…”

“…An example of such a characteristic is shown in Figure 10. The T m (f) relationship was successfully described by the Vogel-Fulcher Equation ( 5) [5,33,38,39]:…”

“…The admixture of praseodymium ions significantly reduces the activation energy associated with the reorientation of the dipole moments while increasing the freezing temperature T m . Considering the increase in the T f temperature value and the decrease in the T dev temperature value, it can be concluded that the temperature range of the occurrence of properties typical for ferroelectric relaxers becomes narrower [33,40].…”