The analysis of the electrical properties of BLT ceramics fabricated from sol-gel derived powders

The (Ba_xLa_1?x)Ti_1?x/4O₃ (BLT,0.001 ≤ x ≤ 0.005) amorphous gel was prepared by sol-gel process. The electricalproperties of obtained materials has been investigated by impedance spectroscopy. Detailedanalysis of impedance spectra allowed to propose an adequate equivalent circuit, whichdescribed the electric properties of discussed materials very well. Basing on the obtainedcircuits and the fitting procedure the grain and grain boundary resistivity was determinedas a function of temperature and La concentration. With increase of La admixture thecontribution of grain and grains impedance to the bulk impedance changes. It was foundthat the small amount of La additive decreases the blocking factor of the grain boundaryin the temperature range 600–850 K, whereas the amount of La on the level of 0.4–0.5 mol.%causes the sharp increase of the mentioned factor. The fact may be attributed to adecrease of grain activation energy and increase of the grain boundary one.