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8 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on NaTaO3 by Materials Project

NaTaO3 is Orthorhombic Perovskite structured and crystallizes in the orthorhombic Pna2_1 space group. The structure is three-dimensional. Na1+ is bonded in a 9-coordinate geometry to eight O2- atoms. There are a spread of Na–O bond distances ranging from 2.44–2.76 Å. Ta5+ is bonded to six O2- atoms to form corner-sharing TaO6 octahedra. The corner-sharing octahedra tilt angles range from 20–21°. There is one shorter (1.99 Å) and five longer (2.00 Å) Ta–O bond length. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a 5-coordinate geometry to three equivalent Na1+ and two equivalent Ta5+ atoms. In the second O2- site, O2- is bonded in a 5-coordinate geometry to three equivalent Na1+ and two equivalent Ta5+ atoms. In the third O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Na1+ and two equivalent Ta5+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NaTaO3 by Materials Project

NaTaO3 crystallizes in the tetragonal P4/mbm space group. The structure is three-dimensional. there are two inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are four shorter (2.55 Å) and four longer (2.77 Å) Na–O bond lengths. In the second Na1+ site, Na1+ is bonded in a 12-coordinate geometry to eight O2- atoms. There are four shorter (2.55 Å) and four longer (2.77 Å) Na–O bond lengths. Ta5+ is bonded to six O2- atoms to form corner-sharing TaO6 octahedra. The corner-sharing octahedra tilt angles range from 0–21°. All Ta–O bond lengths are 2.00 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Na1+ and two equivalent Ta5+ atoms. In the second O2- site, O2- is bonded in a distorted linear geometry to four Na1+ and two equivalent Ta5+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NaTaO3 by Materials Project

NaTaO3 is Orthorhombic Perovskite structured and crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. there are two inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded in a 12-coordinate geometry to twelve O2- atoms. There are a spread of Na–O bond distances ranging from 2.43–3.07 Å. In the second Na1+ site, Na1+ is bonded in a 10-coordinate geometry to ten O2- atoms. There are a spread of Na–O bond distances ranging from 2.57–2.95 Å. Ta5+ is bonded to six O2- atoms to form corner-sharing TaO6 octahedra. The corner-sharing octahedra tilt angles range from 17–24°. All Ta–O bond lengths are 2.00 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to four Na1+ and two equivalent Ta5+ atoms. In the second O2- site, O2- is bonded in a 5-coordinate geometry to three Na1+ and two equivalent Ta5+ atoms. In the third O2- site, O2- is bonded in a 4-coordinate geometry to four Na1+ and two equivalent Ta5+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NaTaO3 by Materials Project

NaTaO3 crystallizes in the cubic Fd-3m space group. The structure is three-dimensional. Na1+ is bonded in a hexagonal planar geometry to six equivalent O2- atoms. All Na–O bond lengths are 2.65 Å. Ta5+ is bonded to six equivalent O2- atoms to form corner-sharing TaO6 octahedra. The corner-sharing octahedral tilt angles are 43°. All Ta–O bond lengths are 2.00 Å. O2- is bonded in a 4-coordinate geometry to two equivalent Na1+ and two equivalent Ta5+ atoms.

36 MATERIALS SCIENCE↗
NASA NTRS1974

Alkali oxide-tantalum oxide and alkali oxide-niobium oxide ionic conductors

A search was made for new cationic conducting phases in alkali-tantalate and niobate systems. The phase equilibrium diagrams were constructed for the six binary systems Nb2O5-LiNbO3, Nb2O5-NaNbO3, Nb2O5-KNbO3, Ta2O5-NaTaO3, Ta2O5-LiTaO3, and Ta2O5-KTaO3. Various other binary and ternary systems were also examined. Pellets of nineteen phases were evaluated (by the sponsoring agency) by dielectric loss measurements. Attempts were made to grow large crystals of eight different phases. The system Ta2O5-KTaO3 contains at least three phases which showed peaks in dielectric loss vs. temperature. All three contain structures related to the tungsten bronzes with alkali ions in non-stoichiometric crystallographic positions.

Roth, R. S.↗
NASA NTRS1977

Susceptibility to hot corrosion of four nickel-base superalloys, NASA-TRW VIA, B-1900, 713C and IN-738

The susceptibility to hot corrosion of four nickel-base, cast superalloys has been studied at 900 and 1000 C. The test consisted of coating alloy samples with known amounts of Na2SO4 and oxidizing the coated samples isothermally in 1 atmosphere of slowly flowing oxygen, the weight-gain being monitored on a sensitive recording microbalance. Susceptibility to hot corrosion decreased in the order of decreasing molybdenum content of the alloys. Preoxidation of samples before hot-corrosion testing markedly increased the induction period observed prior to the inception of hot corrosion for all alloys tested. X-ray diffraction analyses of the oxide scales were made. All samples that underwent hot corrosion showed the presence of a (Ni,Co)MoO4 layer near the alloy-oxide interface. Several specimens displayed resistance to hot corrosion and these showed NaTaO3 as a prominent feature in their oxide scale. Our results may be interpreted as indicating that molybdenum in an alloy is detrimental, with respect to hot corrosion, while tantalum is beneficial.

Stearns, C. A.↗
NASA NTRS1977

Mechanism of beneficial effect of tantalum in hot corrosion of nickel-base superalloys

X-ray diffraction and electron microprobe analyses were used to examine a prominent NaTaO3 pattern formed in a number of nickel-base superalloys. It is found that a beneficial effect of tantalum with respect to hot corrosion attack arises from the ability of Ta2O5 to tie up Na2O and prevent the formation of a molten Na2MoO4 phase.

Fryburg, G. C.↗