Supercritical hydrothermal synthesis of highly crystalline lanthanum zirconate nanoparticles

• Published in: The Journal of supercritical fluids Vol. 143; pp. 134 - 138
• Main Authors: Hojo, Daisuke, Ohara, Hiroaki, Aida, Tsutomu, Seong, Gimyeong, Aoki, Nobuaki, Takami, Seiichi, Adschiri, Tadafumi
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.01.2019
• Subjects: La2Zr2O7; Nanoparticles; pH-controlled dissolution; Phyrochlore; Supercritical hydrothermal; Nanoparticles; Supercritical hydrothermal; pH-controlled dissolution; Phyrochlore; La2Zr2O7
• ISSN: 0896-8446; 1872-8162
• DOI: 10.1016/j.supflu.2018.07.004

[Display omitted] •La2Zr2O7 nanoparticles were synthesised in supercritical water at 450 °C and pH 11.•Highly crystalline pyrochlore La2Zr2O7 was obtained even under such mild condition.•The dissolution of La(OH)3 and ZrO2 was accelerated at high T and high pH condition.•The reaction time was lower owing to increasing dissolution of the intermediates.•The environmentally benign process serves as a novel synthetic method for La2Zr2O7. Pyrochlore La2Zr2O7 nanoparticles were synthesised in supercritical water at 450 °C under a relatively short reaction time. Compared to traditional methods, e.g. solid-state reactions, hydrothermal methods, highly crystalline pyrochlore La2Zr2O7 nanoparticles were obtained even under such mild conditions. Furthermore, the supercritical hydrothermal synthesis of La2Zr2O7 nanoparticles was highly sensitive to the solution pH employed, as La(OH)3 and ZrO2 were formed instead of La2Zr2O7 at pH 10 or lower. pH-controlled dissolution of La(OH)3 and ZrO2 thus regulated the formation and growth of La2Zr2O7. This environmentally benign supercritical hydrothermal process will serve as a novel synthetic method for the preparation of La2Zr2O7 with replacing conventional processes.