Synthesis, characterization and sintering of fluorite and pyrochlore-type compounds: Pr2Zr2O7, Sm2Zr2O7 and PrSmZr2O7

Abstract

Fluorite and pyrochlore-type compounds (Pr 2 Zr 2 O 7 , Sm 2 Zr 2 O 7 and PrSmZr 2 O 7 ) powders were prepared by glycine nitrate process (GNP) starting from metal (Sm, Pr) nitrate, zirconium chloride and glycine as a fuel. The GNP process at room temperature initially yielded amorphous powders, which crystallized after subsequent calcination to form crystalline ceramics. The formation of well crystalline compounds took place at temperature as low as 950°C. The phase evolution with thermal treatment as well as powder properties such as crystallite size, lattice strain and lattice parameter were studied by X-ray powder diffraction (XRPD) at room temperature. High-density ceramic pellets free of any additives were obtained after compaction of the obtained powders and subsequent sintering at 1600°C for 4 h in air. Sintering behaviour of the synthesized pyrochlore phases was followed with a scanning electron microscope. Hardness of the sintered samples was found to be in range of 8.9 to 9.9 GPa depending of chemical composition.