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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on BaY2F8 by Materials Project

BaY2F8 crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. Ba2+ is bonded in a distorted hexagonal bipyramidal geometry to eight equivalent F1- atoms. All Ba–F bond lengths are 2.69 Å. Y3+ is bonded in a body-centered cubic geometry to eight equivalent F1- atoms. All Y–F bond lengths are 2.31 Å. F1- is bonded in a distorted trigonal non-coplanar geometry to one Ba2+ and two equivalent Y3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on BaY2F8 by Materials Project

BaY2F8 crystallizes in the tetragonal I-4 space group. The structure is three-dimensional. Ba2+ is bonded in a 4-coordinate geometry to eight F1- atoms. There are four shorter (2.54 Å) and four longer (3.06 Å) Ba–F bond lengths. Y3+ is bonded to six F1- atoms to form corner-sharing YF6 octahedra. The corner-sharing octahedral tilt angles are 44°. There are a spread of Y–F bond distances ranging from 2.11–2.28 Å. There are two inequivalent F1- sites. In the first F1- site, F1- is bonded in a distorted bent 150 degrees geometry to one Ba2+ and one Y3+ atom. In the second F1- site, F1- is bonded in a 2-coordinate geometry to one Ba2+ and two equivalent Y3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on BaY2F8 by Materials Project

BaY2F8 crystallizes in the monoclinic Cm space group. The structure is three-dimensional. Ba2+ is bonded to twelve F1- atoms to form face-sharing BaF12 cuboctahedra. There are a spread of Ba–F bond distances ranging from 2.76–2.99 Å. Y3+ is bonded in a 8-coordinate geometry to eight F1- atoms. There are a spread of Y–F bond distances ranging from 2.27–2.35 Å. There are five inequivalent F1- sites. In the first F1- site, F1- is bonded in a 2-coordinate geometry to two equivalent Ba2+ and two equivalent Y3+ atoms. In the second F1- site, F1- is bonded in a distorted trigonal non-coplanar geometry to one Ba2+ and two equivalent Y3+ atoms. In the third F1- site, F1- is bonded in a 3-coordinate geometry to one Ba2+ and two equivalent Y3+ atoms. In the fourth F1- site, F1- is bonded in a distorted trigonal non-coplanar geometry to one Ba2+ and two equivalent Y3+ atoms. In the fifth F1- site, F1- is bonded in a 2-coordinate geometry to two equivalent Ba2+ and two equivalent Y3+ atoms.

36 MATERIALS SCIENCE↗
NASA NTRS1990

New laser materials for laser diode pumping

The potential advantages of laser diode pumped solid state lasers are many with high overall efficiency being the most important. In order to realize these advantages, the solid state laser material needs to be optimized for diode laser pumping and for the particular application. In the case of the Nd laser, materials with a longer upper level radiative lifetime are desirable. This is because the laser diode is fundamentally a cw source, and to obtain high energy storage, a long integration time is necessary. Fluoride crystals are investigated as host materials for the Nd laser and also for IR laser transitions in other rare earths, such as the 2 micron Ho laser and the 3 micron Er laser. The approach is to investigate both known crystals, such as BaY2F8, as well as new crystals such as NaYF8. Emphasis is on the growth and spectroscopy of BaY2F8. These two efforts are parallel efforts. The growth effort is aimed at establishing conditions for obtaining large, high quality boules for laser samples. This requires numerous experimental growth runs; however, from these runs, samples suitable for spectroscopy become available.

Jenssen, H. P.↗
NASA NTRS2018

Mid-infrared Spectroscopy of Pr-Doped Materials

Solid state lanthanide doped lasers primarily operate in the ultraviolet, visible, near infrared and short-wavelength infrared out to around 2.1 μm. At longer wavelengths, the transitions in conventional oxide crystal and glass materials become susceptible to multiphonon quenching due to their relatively large phonon energy. The use of low phonon materials can minimize the nonradiative quenching, opening up possibilities for solid state lanthanide lasers operating in the mid-infrared (MIR). This provides motivation to study the spectroscopy of lanthanide ions in bromide, chloride and fluoride materials, which have relatively low phonon energies. In this article, the MIR spectroscopy or praseodymium ions in five different host materials is studied, specifically KPb2Br5 (KPB), LaF3, KYF4 (KYF), BaY2F8 (BYF) and YLiF4 (YLF) host crystals. The MIR emission cross sections have been measured from 3 to 6 μm and reciprocity of absorption and emission is utilized to validate the results. The lifetime dynamics in the MIR are covered for various pump and emission wavelengths. Results are also presented on MIR emission from 6.5 to 8.5 μm in a Pr: KPB crystal, which, to the best of the authors knowledge, is the first such measurement of luminescence in this wavelength range that has been published.

Brian M Walsh↗