| Abstract [eng] |
In the present thesis the reported results let us to conclude that the developed aqueous sol–gel procedure could be successfully used for the low-temperature synthesis of monophasic perovskite gadolinium aluminate ceramics. It was also demonstrated that the selection of raw materials for the sol–gel processing should be done with care. Monophasic perovskite structure gadolinium aluminate GdAlO3 has been synthesized by sol gel synthesis method at 1000 oC, using gadolinium oxide as gadolinium raw material and 1.2 ethanediol, natural tartaric acid, citric acid or mixture of citric acid and ethanolamine as complexing agent. According to the XRD results, the Gd2O3 instead of Gd(NO3)36H2O preferably should be used as starting material for the preparation of GdAlO3. Monophasic perovskite structure strontium substituted gadolinium aluminate Gd0.90Sr0.10AlO3– was synthesized by the same sol gel synthesis method at 1000 oC, using gadolinium oxide as gadolinium raw material, strontium nitrate as strontium ion source and EDTA as complexing agent. It was proved that better gadolinium ion source is gadolinium oxide than gadolinium nitate hexahydrate, better complexing agent – EDTA than natural tartaric acid in the synthesis of GdAlO3 and strontium substituted Gd1–xSrxAlO3– (x = 0.10, 0.25, 0.50, 0.75) samples. According to the XRD results, increasing amount of strontium reduces amount of peaks of perovskite structure gadolinium aluminate. Besides, 800 ºC temperature is too low for the successful synthesis. An aqueous sol gel synthesis method for lanthanum and gadolinium cobaltates was suggested for the first time to our knowledge. Monophasic perovskite structure lanthanum cobaltate LaCoO3 was synthesized at 1000 oC, using lantanum nitrate as lantanum raw material, strontium nitrate as strontium ion source and 1.2 ethanediol as complexing agent. Despite increasing amount of strontium and different heating time (3 and 10 h) the main phase was detected of LaCoO3 in the La1–xSrxCoO3– (x = 0.25, 0.50, 0.75) samples, heated from 900 ºC. Monophasic perovskite structure gadolinium cobaltate GdCoO3 was synthesized by sol gel method at 700–1200 oC, using gadolinium oxide as gadolinium raw material, strontium nitrate as strontium ion source and EDTA as complexing agent. Perovskite structure gadolinium cobaltate has formed in the GdCoO3 and Gd0.75Sr0.25CoO3– samples, prepared using gadolinium oxide as gadolinium raw material, strontium nitrate as strontium ion source and natural tartaric acid or citric acid as complexing agent and heated at 1000 ºC. However the obtained samples were not monophasic. |
