Materials based on partially stabilized zirconia are widely used as structural non-metallic high-strength and wear-resistant materials, thermal barrier and protective coatings, as well as bioinert materials for medicine. The tetragonal phase of solid solutions based on zirconia is stabilized by doping with yttrium, cerium oxides, or oxides of other rare earth elements.
One of the possible ways to optimize the mechanical characteristics of ZrO2-Y2O3 solid solutions crystals is to partially replace Y2O3 with oxides of other rare-earth elements. This work presents the results of studying the phase composition, structure, and mechanical properties of ZrO2-based crystals stabilized with yttrium oxide and co-doped with neodymium, erbium, or ytterbium oxides with a total concentration of 3.2 mol.%.
The crystals were grown by directional melt crystallization in a cold container. The phase composition of the crystals was determined by X-ray diffractometry and Raman spectroscopy. The crystal structure was investigated by transmission electron microscopy. The microhardness and crack resistance of crystals were measured by the indentation method.
The study of the phase composition and structure of the crystals showed that, while maintaining the total concentration of codoning oxides, a change in the degree of substitution of Y3+ cations for dopant cations affects the quantitative ratio of phases, the degree of their tetragonality, and the size of twins.
The study of the mechanical characteristics of crystals, such as fracture toughness and microhardness, showed that co-doping has an insignificant effect on the change in microhardness values. The value of the crack resistance of crystals increases with an increase in the radius of the rare earth element of the co-doped oxide. The study of the monoclinic phase distribution in the region of the indenter indentation is carried out. Comparison of the obtained data on the dependence of the tetragonal - monoclinic phase transformations intensity with the data on the fracture toughness of crystals shows a general tendency towards a decrease in the values of fracture toughness with a decrease in the intensity of the tetragonal - monoclinic phase transformations.
The work was supported by research grants № 18-13-00397 of the Russian Science Foundation.
Thank you for this nice presentation. May I ask you how you did to conclude to the co-existence of two tetragonal phases with close lattice parameters. Was it done by X-ray diffraction? If yes, were the peaks of the two forms clearly distinguishable ?
I must say that I am very interested in zirconia. I developped a computer program that permits to reconstruct the parent cubic grains from an EBSD map of the monoclinic grains. This program was used for the last years by some geologists to better understand the thermomechanical history of some rocks under impacts (from Moon or Earth). I noticed the co-existence of various orientation relationships (OR) between the parent cubic phase and the monoclinic martensite. I was wondering whether such co-existence of OR also exist in your "artificial" zirconia, and if this could be due to the co-existence of the two forms of tetragonal zirconia, or to the accommodation of the lattice strains induced by the transformation . My lab is equipped with a very good SEM with EBSD and TKD and I was wondering if you could send me some of your samples (and TEM lamella)? In summary, I was wondering if you would accept a collaboration with me.
Kind regards
Cyril Cayron
You are right, two tetragonal phases were determined by X-ray diffraction. A detailed study of the diffraction patterns in the region of large 2θ angles makes it possible to detect these two phases. The peaks are clearly distinguishable. A more detailed description of the results of PSZ crystals research can be found in our articles. For example:
M.A. Borik et al. / Journal of the European Ceramic Society 35 (2015) 1889–1894
M.A. Borik et al. / Journal of Alloys and Compounds 586 (2014) S231–S235
Our laboratory is always open for collaboration. Details of future cooperation can be discussed by e-mail.
Best regards,
Alexey Kulebyakin
e-mail: kulebyakin@lst.gpi.ru
