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DOE OSTI2020

Materials Data on LaVO4 by Materials Project

LaVO4 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. La3+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of La–O bond distances ranging from 2.51–2.99 Å. V5+ is bonded in a tetrahedral geometry to four O2- atoms. There are a spread of V–O bond distances ranging from 1.73–1.75 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a 1-coordinate geometry to two equivalent La3+ and one V5+ atom. In the second O2- site, O2- is bonded in a distorted single-bond geometry to two equivalent La3+ and one V5+ atom. In the third O2- site, O2- is bonded in a 1-coordinate geometry to two equivalent La3+ and one V5+ atom. In the fourth O2- site, O2- is bonded in a distorted single-bond geometry to three equivalent La3+ and one V5+ atom.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on LaVO4 by Materials Project

LaVO4 is Zircon structured and crystallizes in the tetragonal I4_1/amd space group. The structure is three-dimensional. La3+ is bonded in a 8-coordinate geometry to eight equivalent O2- atoms. There are four shorter (2.48 Å) and four longer (2.56 Å) La–O bond lengths. V5+ is bonded in a tetrahedral geometry to four equivalent O2- atoms. All V–O bond lengths are 1.74 Å. O2- is bonded in a 1-coordinate geometry to two equivalent La3+ and one V5+ atom.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Ion beam irradiation of ABO4 compounds with the fergusonite, monazite, scheelite, and zircon structures

The effects of irradiation on CaWO4, SrWO4, BaWO4, YVO4, LaVO4, YNbO4, and LaNbO4 were investigated on thin crystals using 1.0 MeV Kr ions at 50-1000 K. All of the ABO4 compounds can be amorphized with calculated damage cross sections (σa = 1/Fc0) in the range of ~0.30-1.09 × 10-14 cm2 ion-1 at zero Kelvin. The analysis of fluence-temperature data returned critical temperatures for amorphization (Tc) of 311 ± 1, 358 ± 90, 325 ± 19, 415 ± 17, 541 ± 6, 636 ± 26, and 1012 ± 1 K, respectively, for the compounds listed above. Compared with previous in situ irradiation of ABO4 orthophosphate samples using 0.8 MeV Kr ions, the Tc values of LaVO4 and YVO4 are higher than those of LaPO4 and YPO4 by 82 K and 124 K, respectively. The Tc values of the three scheelite structures, CaWO4, SrWO4, and BaWO4, indicate that they are the most radiation tolerant compounds under these conditions. The A-B cation anti-site energies, EfAB, determined by DFT range from 2.48 to 10.58 eV and are highly correlated with the A-B cation ionic radius ratio, rA/rB, but are not correlated with Tc across the different structure types, suggesting that the formation and migration energies of Frenkel defects play a more important role in damage recovery in these compounds. We also discuss the role of cation and anion charge/iconicity as determined by DFT. ABO4 compounds with the zircon structure and B = P or V have a distinct advantage over those with B = Si as the damaged regions do not appear to be significantly affected by polymerization of (PO4) 3- or (VO4) 3- groups which might stabilize the amorphous fraction and ultimately lead to phase separation as observed in zircon (ZrSiO4).

amorphization↗

DOE OSTI2021

Tailoring the Radionuclide Encapsulation and Surface Chemistry of La(223Ra)VO4 Nanoparticles for Targeted Alpha Therapy

The development of targeted alpha therapy (TAT) as a viable cancer treatment requires innovative solutions to challenges associated with radionuclide retention to enhance local tumor cytotoxicity and to minimize off-target effects. Nanoparticles (NPs) with high encapsulation and high retention of radionuclides have shown potential in overcoming these issues. This article shows the influence of pH on the structure of lanthanum vanadate (LaVO4) NPs and its impact on the radiochemical yield of 223Ra and subsequent retention of its decay daughters, 211Pb and 211Bi. An acidic pH (4.9) results in a high fraction of La(223Ra)VO4 NPs with tetragonal structure (44.6–66.1%) and a 223Ra radiochemical yield <40%. Adjusting the pH to 11 yields >80% of La(223Ra)VO4 NPs with monoclinic structure and increases the 223Ra radiochemical yield >85%. The leakage of decay daughters from La(223Ra)VO4 NPs (pH 11) was <5% and <0.5% when exposed to deionized water and phosphate-buffered saline, respectively. Altering the surface chemistry of La(223Ra)VO4 NPs with carboxylate and phosphate compounds resulted in a threefold decrease in hydrodynamic diameter and a 223Ra radiochemical yield between 74.7% and 99.6%. These results show the importance of tailoring the synthesis parameters and surface chemistry of LaVO4 NPs to obtain high encapsulation and retention of radionuclides.

60 APPLIED LIFE SCIENCES↗