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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on LaF3 by Materials Project

LaF3 is alpha bismuth trifluoride structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. La3+ is bonded in a distorted body-centered cubic geometry to fourteen F1- atoms. There are eight shorter (2.54 Å) and six longer (2.93 Å) La–F bond lengths. There are two inequivalent F1- sites. In the first F1- site, F1- is bonded in a 6-coordinate geometry to six equivalent La3+ and eight equivalent F1- atoms. All F–F bond lengths are 2.54 Å. In the second F1- site, F1- is bonded to four equivalent La3+ and four equivalent F1- atoms to form a mixture of face, edge, and corner-sharing FLa4F4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on LaF3 by Materials Project

LaF3 crystallizes in the hexagonal P6_322 space group. The structure is three-dimensional. there are two inequivalent La3+ sites. In the first La3+ site, La3+ is bonded in a 4-coordinate geometry to twelve F1- atoms. There are a spread of La–F bond distances ranging from 2.39–2.98 Å. In the second La3+ site, La3+ is bonded in a 4-coordinate geometry to twelve F1- atoms. There are a spread of La–F bond distances ranging from 2.39–2.98 Å. There are three inequivalent F1- sites. In the first F1- site, F1- is bonded to six La3+ and six equivalent F1- atoms to form face-sharing FLa6F6 cuboctahedra. All F–F bond lengths are 2.57 Å. In the second F1- site, F1- is bonded in a trigonal planar geometry to three La3+ atoms. In the third F1- site, F1- is bonded in a 1-coordinate geometry to four La3+ and one F1- atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on LaF3 by Materials Project

LaF3 is alpha bismuth trifluoride structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. La3+ is bonded to twelve F1- atoms to form LaF12 cuboctahedra that share corners with four equivalent LaF12 cuboctahedra, corners with eight equivalent FLa4F8 cuboctahedra, corners with sixteen equivalent FLa4F4 tetrahedra, edges with eight equivalent LaF12 cuboctahedra, edges with eight equivalent FLa4F4 tetrahedra, faces with four equivalent LaF12 cuboctahedra, and faces with six equivalent FLa4F8 cuboctahedra. There are eight shorter (2.56 Å) and four longer (2.75 Å) La–F bond lengths. There are two inequivalent F1- sites. In the first F1- site, F1- is bonded to four equivalent La3+ and four equivalent F1- atoms to form distorted FLa4F4 tetrahedra that share corners with eight equivalent LaF12 cuboctahedra, corners with eight equivalent FLa4F8 cuboctahedra, corners with eight equivalent FLa4F4 tetrahedra, edges with four equivalent LaF12 cuboctahedra, edges with four equivalent FLa4F8 cuboctahedra, edges with twelve equivalent FLa4F4 tetrahedra, and faces with six equivalent FLa4F4 tetrahedra. All F–F bond lengths are 2.56 Å. In the second F1- site, F1- is bonded to four equivalent La3+ and eight equivalent F1- atoms to form distorted FLa4F8 cuboctahedra that share corners with four equivalent FLa4F8 cuboctahedra, corners with eight equivalent LaF12 cuboctahedra, corners with sixteen equivalent FLa4F4 tetrahedra, edges with eight equivalent FLa4F8 cuboctahedra, edges with eight equivalent FLa4F4 tetrahedra, faces with four equivalent FLa4F8 cuboctahedra, and faces with six equivalent LaF12 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on LaF3 by Materials Project

LaF3 crystallizes in the hexagonal P6_3cm space group. The structure is three-dimensional. La3+ is bonded in a 10-coordinate geometry to ten F1- atoms. There are a spread of La–F bond distances ranging from 2.42–2.87 Å. There are four inequivalent F1- sites. In the first F1- site, F1- is bonded in a trigonal planar geometry to three equivalent La3+ atoms. In the second F1- site, F1- is bonded in a distorted trigonal non-coplanar geometry to three equivalent La3+ atoms. In the third F1- site, F1- is bonded in a distorted trigonal planar geometry to three equivalent La3+ atoms. In the fourth F1- site, F1- is bonded in a 2-coordinate geometry to four equivalent La3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on LaF3 by Materials Project

LaF3 crystallizes in the orthorhombic Cmme space group. The structure is three-dimensional. there are two inequivalent La3+ sites. In the first La3+ site, La3+ is bonded to twelve F1- atoms to form a mixture of face, edge, and corner-sharing LaF12 cuboctahedra. There are a spread of La–F bond distances ranging from 2.53–2.79 Å. In the second La3+ site, La3+ is bonded in a 10-coordinate geometry to ten F1- atoms. There are a spread of La–F bond distances ranging from 2.37–2.92 Å. There are four inequivalent F1- sites. In the first F1- site, F1- is bonded to four La3+ atoms to form a mixture of distorted edge and corner-sharing FLa4 tetrahedra. In the second F1- site, F1- is bonded in a 12-coordinate geometry to four La3+ atoms. In the third F1- site, F1- is bonded in a distorted linear geometry to two equivalent La3+ atoms. In the fourth F1- site, F1- is bonded in a 3-coordinate geometry to four La3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on LaF3 by Materials Project

LaF3 crystallizes in the trigonal P-3c1 space group. The structure is three-dimensional. La3+ is bonded in a 9-coordinate geometry to nine F1- atoms. There are a spread of La–F bond distances ranging from 2.43–2.65 Å. There are three inequivalent F1- sites. In the first F1- site, F1- is bonded in a distorted trigonal planar geometry to three equivalent La3+ atoms. In the second F1- site, F1- is bonded in a 3-coordinate geometry to three equivalent La3+ atoms. In the third F1- site, F1- is bonded in a trigonal planar geometry to three equivalent La3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on LaF3 by Materials Project

LaF3 is Sodium arsenide structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. La3+ is bonded in a 5-coordinate geometry to eleven F1- atoms. There are five shorter (2.42 Å) and six longer (2.73 Å) La–F bond lengths. There are two inequivalent F1- sites. In the first F1- site, F1- is bonded in a 1-coordinate geometry to four equivalent La3+ atoms. In the second F1- site, F1- is bonded in a trigonal planar geometry to three equivalent La3+ atoms.

36 MATERIALS SCIENCE↗
NASA NTRS1976

LaF3 infrared detector

A class of infrared detectors is proposed, and experimental results are presented for a prototype device. The material used is LaF3, an ionic conductor with a capacitance that varies exponentially with temperature. The detectivity of a prototype detector is estimated from measured signal voltages and incident power, and a Johnson noise voltage is calculated from the measured resistance. At a modulation frequency of 20 Hz, the estimated detectivity is about 2 million cm/sq root Hz/W. For the parameters characterizing this device, the estimated detectivity is consistent with a theoretical prediction. The theory further predicts an optimum detectivity of about 1 billion cm/sq root Hz/W for much thinner devices than the prototypes.

Sher, A.↗
NASA NTRS1979

LaF3 insulators for MIS structures

Thin films of LaF3 deposited on Si or GaAs substrates have been observed to form blocking contacts with very high capacitances. This results in comparatively hysteresis-free and sharp C-V (capacitance-voltage) characteristics for MIS structures. Such structures have been used to study the interface states of GaAs with increased resolution and to construct improved photocapacitive infrared detectors.

Sher, A.↗
NASA NTRS1984

Surface tension of ZrF4-BaF2-LaF3 glass

A solidified pendant drop technique is presently used in the measurement of surface tension of a 62 mol pct ZrF4, 33 mol pct BaF2, 5 mol pct LaF3 heavy metal-fluoride glass, in keeping with a requirement from a comparison experiment planned for microgravity conditions aboard the Space Shuttle. The surface tension at 550 C is 0.174 + or - 0.005 J/sq m.

Bansal, N. P.↗
NASA NTRS1990

Vacuum ultraviolet thin films. I - Optical constants of BaF2, CaF2, LaF3, MgF2, Al2O3, HfO2, and SiO2 thin films. II - Vacuum ultraviolet all-dielectric narrowband filters

An iteration process matching calculated and measured reflectance and transmittance values in the 120-230 nm VUV region is presently used to ascertain the optical constants of bulk MgF2, as well as films of BaF2, CaF2, LaF3, MgF2, Al2O3, HfO2, and SiO2 deposited on MgF2 substrates. In the second part of this work, a design concept is demonstrated for two filters, employing rapidly changing extinction coefficients, centered at 135 nm for BaF2 and 141 nm for SiO2. These filters are shown to yield excellent narrowband spectral performance in combination with narrowband reflection filters.

Zukic, Muamer↗
NASA NTRS1994

Red-to-violet and near-infrared-to-green energy upconversion in LaF3:Er(3+)

When the (sup 4)F(sub 9/2) state was resonantly excited, emission was detected from the higher states (sup 4)S(sub 3/2)((sup 2)H(sub 11/2), (sup 4)G(sub 11/2), and (sup 2)P(sub 3/2) in addition to the resonant emission. Two- and three-photon processes were found to be responsible in populating the (sup 4)S(sub 3/2) and the (sup 2)P(sub 3/2) states, respectively. Energy upconversion efficiencies into the (sup 4)S(sub 3/2) and the (sup 2)P(sub 3/2) states were found to be 7.2 x 10(exp -3) and 1.4 x 10(exp -4), respectively. When the (sup 4)I(sub 9/2) state was resonantly excited we detected green emission from the (sup 4)S(sub 3/2)((sup 2)H(sub 11/2)). The energy upconversion efficiency of this process was found to be 1.4 x 10(exp -3).

Reddy, B. R.↗
NASA NTRS1981

Insulators for Pb(1-x)Sn(x)Te

Thin films of LaF3 were e-gun and thermally deposited on several substrates. The e-gun deposited films are fluorine deficient, have high ionic conductivities that persist to 77 K, and high effective dielectric constants. The thermally deposited material tends to be closer to stoichiometric, and have higher effective breakdown field strengths. Thermally deposited LaF3 films with resistivities in excess of 10 to the 12th power ohms - cm were deposited on metal coated glass substrates. The LaF3 films were shown to adhere well to PbSnTe, surviving repeated cycles between room temperature and 77 K. The LaF3 films on GaAs were also studied.

Tsuo, Y. H.↗
NASA NTRS1994

Development of infrared sensors using energy transfer/energy upconversion processes: Study of laser excited fluorescence in rare Earth ion doped crystals

A summary is presented of the spectroscopic study of three systems: LaF3:Ho(3+), LaF3:Er(3+) and CaF2:Nd(3+). When the D levels of Ho(3+) in LaF3 were resonantly excited with a laser beam of 640 nm, upconverted emissions were detected from J (416 nm), F (485 nm), and E (546 nm) levels. Energy upconverted emissions were also observed from F and E levels of Ho(3+) when the material was excited with an 800 nm near infrared laser. When the D levels of Er(3+) in LaF3 were resonantly excited with a laser beam of 637 nm, upconverted emissions were detected from the E (540 nm) and P (320, 400, and 468 nm) levels. Energy upconverted emissions were also observed from F, E, and D levels of Er(3+) when the material was resonantly excited with an 804 nm near infrared laser. When the D levels of Nd(3+) in CaF2 were resonantly excited with a laser beam of 577 nm, upconverted emissions were detected from the L (360 and 382 nm), K (418 nm), and I (432 nm) levels. Very weak upconverted emissions were detected when this system was irradiated with a near infrared laser. The numbers in parentheses are the wavelengths of the emissions.

Nash-Stevenson, S. K.↗
NASA NTRS1974

Some metal-graphite and metal-ceramic composites for use as high energy brake lining materials

Materials were studied as candidates for development as potential new aircraft brake lining materials. These families were (1) copper-graphite composites; (2) nickel-graphite composites; (3) copper - rare-earth-oxide (gadolinium oxide (Gd2O3) or lanthanum oxide (La2O3)) composites and copper - rare-earth-oxide (La2O3) - rare-earth-fluoride (lanthanum fluoride (LaF3)) composites; (4) nickel - rare-earth-oxide composites and nickel - rare-earth-oxide - rare-earth-fluoride composites. For comparison purposes, a currently used metal-ceramic composite was also studied. Results showed that the nickel-Gd2O3 and nickel-La2O3-LaF3 composites were comparable or superior in friction and wear performance to the currently used composite and therefore deserve to be considered for further development.

Bill, R. C.↗