Synthesis and characterization of pyrochlore lanthanide (Pr, Sm) zirconate ceramics

Three different lanthanide zirconate powders: Pr2Zr2O7, Sm2Zr2O7 and PrSmZr2O7 were prepared by combustion synthesis. The synthesis initially yielded amorphous powders, which crystallized after subsequent thermal treatment. Well-crystallized compounds were formed after calcination at temperature as low as 950 °C. Effect of the thermal treatment on the phase evolution was studied by X-ray powder diffraction (XRD). The powders calcined at the highest temperature (1550 °C) showed that all compositions possess the pyrochlore structure with the space group No. 227. The obtained powders were compacted and pressureless sintered without additive at 1600 °C for 4 h in the air. Microstructure development was examined by field emission scanning electron microscopy, as well as by transmission electron microscopy. It was found that the lowest value for thermal conductivity, 1.2 W/m K, was obtained for mixed lanthanide composition with pyrochlore structure (PrSmZr2O7). The effect of chemical composition on micro-hardness and thermal conductivity of the obtained zirconates was studied. © 2019 Elsevier Lt