Pokhrel Madhab, Gupta Santosh K, Wahid Kareem, Mao Yuanbing
Department of Chemistry , University of Texas Rio Grande Valley , 1201 West University Drive , Edinburg , Texas 78539 , United States.
Department of Physics , University of Texas Rio Grande Valley , 1201 West University Drive , Edinburg , Texas 78539 , United States.
Inorg Chem. 2019 Jan 22;58(2):1241-1251. doi: 10.1021/acs.inorgchem.8b02728. Epub 2019 Jan 7.
Complex oxides of the REHfO series are functional materials that exist in the fluorite or pyrochlore phase depending on synthesis method and calcination temperature. In this study, we investigate the process of synthesis, crystal structure stabilization, and phase transition in a series of RE hafnate compounds, synthesized by the coprecipitation process of a single-source complex hydroxide precursor followed with direct calcination or molten-salt synthesis (MSS) method. Phase pure REHfO (RE = Y, La, Pr, Gd, Er, and Lu) ultrafine nanostructured powders were obtained after calcinating the precursor in a molten salt at 650 °C for 6 h. Moreover, we demonstrate that the MSS method can successfully stabilize ideal pyrochlore structures for LaHfO and PrHfO in the nanodomain, which is not possible to achieve by direct calcination of the coprecipitated precursor at 650 °C. We propose mechanisms to elucidate the differences in these two synthesis methods and highlight the superiority of the MSS method for the production of RE hafnate nanoparticles.
REHfO系列复合氧化物是功能材料，其存在萤石相或烧绿石相，这取决于合成方法和煅烧温度。在本研究中，我们研究了一系列铪酸稀土化合物的合成过程、晶体结构稳定化和相变，这些化合物通过单源复合氢氧化物前驱体的共沉淀过程，随后采用直接煅烧或熔盐合成（MSS）方法制备。在650℃的熔盐中煅烧前驱体6小时后，获得了相纯的REHfO（RE = Y、La、Pr、Gd、Er和Lu）超细纳米结构粉末。此外，我们证明，MSS方法能够成功地在纳米域中稳定LaHfO和PrHfO的理想烧绿石结构，而通过在650℃直接煅烧共沉淀前驱体是无法实现这一点的。我们提出了一些机制来解释这两种合成方法的差异，并强调了MSS方法在制备铪酸稀土纳米颗粒方面的优越性。
