| Abstract [eng] |
The aim of this work was to investigate electrical conductivity of new La0.33NbO3, La0.33TaO3, Nd0.33TaO3, Nd0.33NbO3, Pr0.33NbO3, Pr0.33TaO3 ceramics with perovskite structure. Impedance spectroscopy in the frequency range from 10 Hz up to 2 MHz was used for the study, the temperature of the samples was changed in the range from 300 K to 800 K. Two relaxation type dispersion regions were observed in the impedance spectra, which correspond to large ion (La3+, Nd3+ or Pr3+) mobility in the perovskite framework. Bulk and grain boundary conductivities were determined and from their temperature dependencies the activation energies were calculated. 3 conclusions were drawn from these results. First of all, La0.33NbO3 has the highest ionic conductivity of the materials studied. Its crystalline conductivity at 300 K is σkr = 4,12 × 10-5 S/m. Secondly, perovskite structure materials (ABX3) with Nb at the B-position lead to better conditions for ion migration compared to materials containing Ta at the B-position. Finally, the ionic conductivity of the investigated materials increases with increasing temperature but the activation energy decreases. This indicates that at lower temperatures the ions are less delocalised, which may lead to higher values of the electrostriction coefficient. |
