Investigation of the microstructure of the fine-grained YPO4_4:Gd ceramics with xenotime structure after Xe irradiation

The paper reports on the preparation of xenotime-structured ceramics by the Spark Plasma Sintering (SPS) method. Phosphates Y$_{0.95}$Gd$_{0.05}$PO$_4$ (YPO$_4$:Gd) were obtained by the sol-gel method. The synthesized nanopowders are collected in large agglomerates 10-50 mkm in size. Ceramics has a fine-grained microstructure and a high relative density (98.67%). The total time of the SPS process was approximately 18 min. High-density sintered ceramics YPO$_4$:Gd with a xenotime structure were irradiated with Xe$^{+26}$ ions (E = 167 MeV) to fluences of $1\times10^{12}$-$3\times 10^{13}$ cm$^{-2}$. Complete amorphization at maximum fluence was not achieved. As the fluence increases, an insignificant increase in the depth of the amorphous layer is observed. According to the results of grazing incidence XRD (GIXRD), with an increase in fluence from $1\times10^{12}$-$3\times 10^{13}$ cm$^{-2}$, an increase in the volume fraction of the amorphous structure from 20 to 70% is observed. The intensity of XRD peak 200 YPO$_4$:Gd after recovery annealing (700$^\circ$C, 18 h) reached a value of ~80% of the initial intensity I0.Comment: 16 pages, 10 figure

X-Ray Diffraction Analysis of Ceramics Irradiated with High-Energy Ions

NaNd(WO4)2 and NaNd(MoO4)2 ceramic samples subjected to ion implantation is considered. The degree of amorphization of the near-surface layer of the samples depending on the fluence were obtained. The depth of the amorphized layer was also investigated.Рентгенодифракционные исследования образцов до и после облучения выполнялись в лаборатории диагностики радиационных дефектов в твердотельных наноструктурах ИФМ РАН при поддержке Министерства науки и высшего образования РФ (г/з № 0030-2021-0030). Исследование выполнено при финансовой поддержке РФФИ в рамках научного проекта №20-21-00145_Росатом

(Na, Zr) and (Ca, Zr) Phosphate-molybdates and phosphate-tungstates: I–synthesis, sintering and characterization

This article belongs to the Special Issue Inorganic Functional Materials: Synthesis, Characterization and Application.Submicron-grade powders of Na1-xZr2(PO4)3-x(XO4)x compounds (hereafter referred to as NZP) and Ca1-xZr2(PO4)3-x(XO4)x compounds (hereafter, CZP), X = Mo, W (0 ≤ x ≤ 0.5) were obtained by sol-gel synthesis. The compounds obtained were studied by X-ray diffraction phase analysis and electron microscopy. An increase in the W or Mo contents was shown to result in an increase in the unit cell volume of the NZP and CZP crystal lattices and in a decrease in the coherent scattering region sizes. Thermal expansion behavior at high temperatures of synthesized NZP and CZP compounds has been investigated. The dependencies of the parameters a and c on the heating temperature, as well as the temperature dependence of the crystal lattice unit cell volume V in the range from the room temperature up to 800 °C, were obtained. The dependencies of the average thermal expansion coefficient (αav) and of the volume coefficient (β) on the W and Mo contents in the compositions of NZP and CZP compounds were studied. Ceramics Na1-xZr2(PO4)3-x(XO4)x with relatively high density (more than 97.5%) were produced by spark plasma sintering (SPS). The increase in the W or Mo contents in the ceramics leads to an increase in the relative density of NZP and to a decrease of the optimum sintering temperature. The mean grain size in the NZP ceramics decreases with increasing W or Mo contents. The study of strength characteristics has revealed that the hardness of the NZP ceramics is greater than 5 GPa, and that the minimum fracture toughness factor was 1 MPa·m1/2.This research was funded by Russian Science Foundation (Grant No. 21-13-00308). The TEM study of the powders was carried out on the equipment of the Center for Collective Use “Materials Science and Metallurgy” (National University of Science and Technology “MISIS”, Moscow, Russia) with the financial support of the Ministry of Science and Higher Education of the Russian Federation (Grant No. 075-15-2021-696). The XRD investigations of the specimens were carried out in the Laboratory of Diagnostics of Radiation Defects in Solid State Nanostructures at the Institute for Physics of Microstructures RAS (IPM RAS, Nizhny Novgorod, Russia) with the financial support of the Ministry of Science and Higher Education of the Russian Federation (Grant No. 0030-2021-0030).Peer reviewe

Morphology and Structure of Defected Niobium Oxide Nonuniform Arrays Formed by Anodizing Bilayer Al/Nb Systems

The work is devoted to the X-ray diffraction research of defected niobium oxide nonuniform (NON) arrays and niobium oxide nanocolumns formed by electrochemical anodizing. The obtained results allow to make an assumption about the probable presence of a significant amount of NbO, NbO0.7, Nb2O5 and a small amount of NbO2, and Al in the composition of defected NON and the presence of all these substances in the nanocolumns of niobium oxide except NbO0.7, but in smaller quantities. The comparative analysis of the NON structure and the nanocolumns makes it possible to isolate, probably, a significant amount of Nb0.94O0.06, Nb6O in the defected nanocolumns, which was not found in NON