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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on NaVO3 by Materials Project

NaVO3 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. there are two inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded to six O2- atoms to form NaO6 octahedra that share corners with six equivalent VO4 tetrahedra and edges with five NaO6 octahedra. There are a spread of Na–O bond distances ranging from 2.38–2.47 Å. In the second Na1+ site, Na1+ is bonded to six O2- atoms to form distorted NaO6 octahedra that share corners with four equivalent VO4 tetrahedra, edges with three equivalent NaO6 octahedra, and edges with two equivalent VO4 tetrahedra. There are a spread of Na–O bond distances ranging from 2.38–2.70 Å. V5+ is bonded to four O2- atoms to form VO4 tetrahedra that share corners with five NaO6 octahedra, corners with two equivalent VO4 tetrahedra, and an edgeedge with one NaO6 octahedra. The corner-sharing octahedra tilt angles range from 31–66°. There are a spread of V–O bond distances ranging from 1.67–1.83 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a 2-coordinate geometry to one Na1+ and two equivalent V5+ atoms. In the second O2- site, O2- is bonded in a distorted T-shaped geometry to two Na1+ and one V5+ atom. In the third O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to three Na1+ and one V5+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NaVO3 by Materials Project

NaVO3 is (Cubic) Perovskite structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Na1+ is bonded to twelve equivalent O2- atoms to form NaO12 cuboctahedra that share corners with twelve equivalent NaO12 cuboctahedra, faces with six equivalent NaO12 cuboctahedra, and faces with eight equivalent VO6 octahedra. All Na–O bond lengths are 2.67 Å. V5+ is bonded to six equivalent O2- atoms to form VO6 octahedra that share corners with six equivalent VO6 octahedra and faces with eight equivalent NaO12 cuboctahedra. The corner-sharing octahedral tilt angles are 0°. All V–O bond lengths are 1.89 Å. O2- is bonded in a distorted linear geometry to four equivalent Na1+ and two equivalent V5+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NaVO3 by Materials Project

Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

36 MATERIALS SCIENCE↗
NASA NTRS1985

Ceramic oxide reactions with V2O5 and SO3

Ceramic oxides are not inert in combustion environments, but can react with, inter alia, SO3, and Na2SO4 to yield low melting mixed sulfate eutectics, and with vanadium compounds to produce vanadates. Assuming ceramic degradation to become severe only when molten phases are generated in the surface salt (as found for metallic hot corrosion), the reactivity of ceramic oxides can be quantified by determining the SO3 partial pressure necessary for molten mixed sulfate formation with Na2SO3. Vanadium pentoxide is an acidic oxide that reacts with Na2O, SO3, and the different ceramic oxides in a series of Lux-Flood type of acid-base displacement reactions. To elucidate the various possible vanadium compound-ceramic oxide interactions, a study was made of the reactions of a matrix involving, on the one axis, ceramix oxides of increasing acidity, and on the other axis, vanadium compounds of increasing acidity. Resistance to vanadium compound reaction increased as the oxide acidity increased. Oxides more acidic than ZrO2 displaced V2O5. Examination of Y2O3- and CeO2-stabilized ZrO2 sintered ceramics which were degraded in 700 C NaVO3 has shown good agreement with the reactions predicted above, except that the CeO2-ZrO2 ceramic appears to be inexplicably degraded by NaVO3.

Jones, R. L.↗
NASA NTRS1985

Destabilization of yttria-stabilized zirconia induced by molten sodium vanadate-sodium sulfate melts

The extent of surface destabilization of ZrO2 - 8 wt percent Y2O3 ceramic disks was determined after exposure to molten salt mixtures of sodium sulfate containing up to 15 mole percent sodium metavanadate (NaVO3) at 1173 K. The ceramic surface was observed to transform from the cubic/tetragonal to monoclinic phase, concurrent with chemical changes in the molten salt layer in contact with the ceramic. Significant attack rates were observed in both pure sulfate and metavanadate sulfate melts. The rate of attack was found to be quite sensitive to the mole fraction of vanadate in the molten salt solution and the partial pressure of sulfur trioxide in equilibrium with the salt melt. The observed parabolic rate of attack is interpreted to be caused by a reaction controlled by diffusion in the salt that penetrates into the porous layer formed by the destabilization. The parabolic rate constant in mixed sodium metavanadate - sodium sulfate melts was found to be proportional to the SO3 partial pressure and the square of the metavanadate concentration. In-situ Raman spectroscopic measurements allowed simultaneous observations of the ceramic phases and salt chemistry during the attack process.

Nagelberg, A. S.↗