Novel Routes for Sintering of Ultra-high Temperature Ceramics and their Properties
Final rept. 2 Nov 2011-31 Oct 2014
NATIONAL ACADEMY OF SCIENCES (UKRAINE) FRANTZEVICH INST FOR PROBLEMS IN MATERIALS SCIENCE
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The project has been focused on phase equilibria research, development of phase diagrams of the ternary systems ZrO2-CeO2- Ln2O3LnLa2O3,Eu2O3,Gd2O3 and some of boundary binary systems, as well as manufacturing and characterization of dense, optically transparent ceramics based on LaYO3 and Y3Al5O12 phases. First developed phase diagrams of the ternary systems Zr 2- eO2-Ln2O3 Ln La, Eu, Gd and binary systems ZrO2-Gd2O3, CeO2-Gd2O3, CeO2-Eu2O3 have been presented as a collection of isothermal and polythermal sections in the temperature range from 600 to 1500 deg C. The solubility of components, extension of one, two and three phase fields and mechanisms of phase reactions have been determined. Lattice parameters for solid solutions were calculated. The results have been summarized along the rows of the systems ZrO2-Ln2O3, CeO2-Ln2O3 and Zr 2- eO2-Ln2O3. The pyrochlore-type or defect fluorite-type phases of the formulae ZrCe2Gd2O7 when doped with scintillator Eu2represent a subject of interest for future ceramic laser matrices. The nanosize powders of doped NdYbLaYO3 and NdY3Al5O12 phases containing various amount of dopants have been chemically prepared. Particle size distribution was narrow in the particle size range of 10-22 nm. Coarsening of particles to 300 nm and faceting of particles were carried out to allow manipulation in strong magnetic field using EPD or SC techniques. The neodymia doped garnet samples showed residual porosity less than 0.2 with good transparency of 70-72 after RCS. Neodymiadopant led to instability of the LaYO3 phase. The rear earth ions such as Er3 and Yb3may be used as laser dopants. The YbLaYO3 ceramics textured under strong magnetic field has shown density of 99.0-99.2. The samples were found semitransparent average transparency is less than 45, but more transparent along c-axis.
- Physical Chemistry
- Geology, Geochemistry and Mineralogy
- Ceramics, Refractories and Glass