Characteristics of Phenomena in Powders Type RE₂Zr₂O₇-Al₂O₃ in High Temperature Annealing Conditions

Abstract

The paper presents test results and characterizes the structural stability of powders, which form a mixture of aluminium oxide (Al2O3) and gadolinium, based on rare earth zirconates. This mixture is provided to create thermal barrier coatings (TBCs) by spraying. The purpose of the tests was to determine the influence of temperature on reactions, occurring between those powders within a temperature range from 25°C to 1500°C, while such conditions were to simulate the conditions, which occur during creation of TBCs and they give an answer to the question concerning mutual reactivity of the powders. The requirements for new materials, provided to spray the TBCs, indicate the necessity to prepare the materials, which do not show tendency towards reactions with the Al2O3, formed during oxidation of Ni (Co) CrAlY, while this reaction is of type bond coat. The tests included differential scanning calorimetric (DSC) analysis and differential thermal analysis (DTA) of powder mixtures. Diffraction analysis was also performed before and after the tests have been finished. The DSC analysis results, obtained at a range of high temperature, did not show any thermal effects, which indicate a low level of mutual reactivity of the powders. However, the DTA analysis suggests presence of such effects at temperature close to 1300°C, and it indicates the necessity to verify exactly the obtained results. Results of the XRD measurement showed that after annealing process already at 1100°C the perovskite oxide of GdAlO3 was present.

Calorimetric study of Eu2O3–ZrO2 feedstock powders and sintered materials

“…; a high coefficient of thermal expansion [10 -5°C-1 ; a working temperature up to 1600°C [9][10][11][12][13]. Recently, some interesting data concerning non-stoichiometric zirconates with fluorite/pyrochlore type of lattice were reported, e.g., better insulating properties [14].…”