Synthesis and thermal properties of zirconate, hafnate and cerate of samarium

Abstract

The basic direction of the development of thermal barrier coatings (TBC) systems is connected with new materials solutions dedicated for bond-coats and ceramic insulating layers. The present article shows the synthesis and thermal properties of different types of insulating ceramic materials based on zirconia, hafnia and ceria. The analyzed materials were synthesized via solid state reaction (SSR) of the mixtures of nanocrystalline feedstock powders of zirconia, hafnia, ceria and samaria. The synthesized materials were analyzed in view of chemical and phase composition. The morphological characterization of the utilized feedstock powders was showed as well. The basic range of the investigation was related to the analysis of thermal parameters such as a thermal diffusivity and coefficient of thermal expansion in temperature range 25 ÷ 1100 °C. The P-type samarium zirconate and hafnate were synthesized as well as F-type non-stoichiometric samarium cerate. The chemical homogeneity of obtained solid materials was satisfactory. The dilatometric measurements showed that Sm2Zr2O7 and Sm2Hf2O7 may be beneficial materials for TBC insulating layer due to the thermal expansion coefficient close to metallic substrate. These materials were also beneficial taking into account the results of thermal diffusivity measurements. In the temperature range 25–1100 °C, samarium hafnate and zirconate were characterized by substantially lower thermal diffusivity compared to that of 8YSZ. In the case of cerate of samarium with fluorite type of structure, the more beneficial thermal properties compared to that of YSZ were observed, however, were considerably less promising related to pyrochlore ceramic materials based on zirconia and hafnia.