Cojocaru Bogdan, Avram Daniel, Negrea Raluca, Ghica Corneliu, Kessler Vadim G, Seisenbaeva Gulaim A, Parvulescu Vasile I, Tiseanu Carmen
Department of Chemistry, University of Bucharest, B-dul Regina Elisabeta, nr. 4-12, 030018 Bucharest, Romania.
National Institute for Laser, Plasma and Radiation Physics, RO 76900 Bucharest-Magurele, Romania.
ACS Omega. 2019 May 22;4(5):8881-8891. doi: 10.1021/acsomega.9b00580. eCollection 2019 May 31.
Technologically relevant tetragonal/cubic phases of HfO can be stabilized at room temperature by doping with trivalent rare earths using various approaches denoted generically as bulk coprecipitation. Using in situ/ex situ X-ray diffraction (XRD), Raman spectroscopy, high-resolution transmission electron microscopy, and in situ/ex situ site-selective, time-gated luminescence spectroscopy, we show that wet impregnation of hafnia nanoparticles with 10% Eu oxide followed by mild calcination in air at 500 °C produces an efficient stabilization of the cubic phase, comparable to that obtained by bulk precipitation. The physical reasons behind the apparently conflictual data concerning the actual crystallographic phase and the local symmetry around the Eu stabilizer and how these can be mediated by luminescence analysis are also discussed. Apparently, the cubic crystal structure symmetry determined by XRD results in a pseudocubic/tetragonal local structure around Eu determined by luminescence. Considering the recent findings on wet impregnated CeO and ZrO, it is concluded that CeO, ZrO, and HfO represent a unique case of a family of oxides that is extremely tolerant to heavy doping by wet impregnation. In this way, the same batch of preformed nanoparticles can be doped with different lanthanide concentrations or with various lanthanides at a fixed concentration, allowing a systematic and reliable investigation of the effect of doping, lanthanide type, and lanthanide concentration on the various functionalities of these technologically relevant oxides.
通过使用统称为体共沉淀的各种方法掺杂三价稀土元素，可在室温下稳定HfO的技术相关四方/立方相。利用原位/非原位X射线衍射（XRD）、拉曼光谱、高分辨率透射电子显微镜以及原位/非原位位点选择性时间分辨发光光谱，我们表明，用10%的氧化铕对氧化铪纳米颗粒进行湿浸渍，然后在500°C的空气中进行温和煅烧，可有效稳定立方相，其效果与通过体沉淀获得的效果相当。我们还讨论了关于实际晶体相以及铕稳定剂周围局部对称性的明显矛盾数据背后的物理原因，以及如何通过发光分析来调节这些原因。显然，由XRD确定的立方晶体结构对称性导致由发光确定的铕周围的伪立方/四方局部结构。考虑到最近关于湿浸渍CeO和ZrO的研究结果，可以得出结论，CeO、ZrO和HfO代表了一类对湿浸渍重掺杂具有极高耐受性的氧化物家族的独特案例。通过这种方式，可以用不同的镧系元素浓度或固定浓度的各种镧系元素对同一批预制纳米颗粒进行掺杂，从而系统可靠地研究掺杂、镧系元素类型和镧系元素浓度对这些技术相关氧化物各种功能的影响。
