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

• Published in: Journal of the European Ceramic Society Vol. 40; no. 7; pp. 2652 - 2657
• Main Authors: Matovic, Branko, Maletaskic, Jelena, Zagorac, Jelena, Pavkov, Vladimir, Maki, Ryosuke S.S., Yoshida, Katsumi, Yano, Toyohiko
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.07.2020
• Subjects: Microstructure; Pyrochlore; Sintering; Synthesis; Thermal conductivity; Pyrochlore; Thermal conductivity; Synthesis; Microstructure; Sintering
• ISSN: 0955-2219; 1873-619X
• DOI: 10.1016/j.jeurceramsoc.2019.11.012

•Nanometric-sized lanthanide zirconate powders were prepared by combustion synthesis.•The crystallite size of samples annealed at temperature up to 1250 °C lies in nanometric range.•A complete conversion to the ordered pyrochlore structure is achieved at 1550 °C.•The obtained, pure powders showed a good sinterability.•High-density ceramic free of any additives was obtained at 1600 °C for 4 h in air. 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.