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1. Ca ₂ Ga ₄ Ge ₆ and Ca ₃ Ga ₄ Ge ₆ : Synthesis, Structure, and Electronic Properties

   https://doi.org/10.1002/zaac.202100342  

   Hodge, Kelsey L; Davis, H Olivia; Koster, Karl G; Windl, Wolfgang; Moore, Curtis E; Goldberger, Joshua E (August 2022, Zeitschrift für anorganische und allgemeine Chemie)

   Abstract During the search for transition metal‐free alkyne hydrogenation catalysts, two new ternary Ca−Ga−Ge phases, Ca₂Ga₄Ge₆(Cmc2₁, a=4.1600(10) Å, b=23.283(5) Å, c=10.789(3) Å) and Ca₃Ga₄Ge₆(C2/m, a=24.063(2) Å, b=4.1987(4) Å, c=10.9794(9) Å, β=91.409(4)°), were discovered. These compounds are isostructural to the previously established Yb₂Ga₄Ge₆and Yb₃Ga₄Ge₆analogues, and according to Zintl‐Klemm counting rules, consist of anionic [Ga₄Ge₆]⁴⁻and [Ga₄Ge₆]⁶⁻frameworks in which every Ga and Ge atom would have a formal octet with no Ga−Ga or Ga−Ge π‐bonding. These compounds are metallic, based on temperature dependent electrical resistivity and thermopower measurements for Ca₃Ga₄Ge₆, along with density functional theory calculations for both phases. Unlike the highly active 13‐layer trigonal CaGaGe phase, these new compounds exhibit minimal activity in the semi/full alkyne hydrogenation of phenylacetylene, which is consistent with previous observations that the lack of a formal octet for framework atoms is essential for catalysis in these Zintl‐Klemm compounds. 

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2. Spectroscopic Evaluation of Er: Ga2Ge5S13 Glass for Mid-IR Laser Applications

   E. Brown; Z. D. Fleischman; J. McKay; U. Hommerich; W. Palosz; S. Trivedi; and M. Dubinskii (July 2022, Optical materials express)

   We present mid-IR spectroscopic characterization of the low-phonon chalcogenide glass, Ga2Ge5S13 (GGS) doped with Er3+ ions. Under the excitation at ∼800 nm, Er3+:GGS exhibited broad mid-IR emission bands centered at ∼2.7, ∼3.5, and ∼4.5 µm at room temperature. The emission lifetime of the 4I9/2 level of Er3+ ions in GGS glass was found to be millisecond-long at room temperature. The measured fluorescence lifetimes were nearly independent of temperature, indicating negligibly small nonradiative decay rate for the 4I9/2 state, as can be expected for a low-maximum-phonon energy host. The transition line-strengths, radiative lifetimes, fluorescence branching ratios were calculated by using the Judd-Ofelt method. The peak stimulated emission cross-section of the 4I9/2 → 4I11/2 transition of Er3+ ion was determined to be ∼0.10×10−20 cm2 at room temperature. 

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3. Comparative study of rare-earth doped low-phonon fluoride and chloride crystals for mid-IR laser potential

   E. Brown, Z. D. (April 2021, Proceedings SPIE 11723, Laser Technology for Defense and Security XVII)

   A comparative study was performed on the mid-infrared emission properties of trivalent erbium (Er3+) and holmium (Ho3+) doped fluorides (BaF2, NaYF4) and ternary chloride-based crystals (CsCdCl3, KPb2Cl5,). All crystals were grown by vertical Bridgman technique. Following optical excitation at 800 nm, all Er3+ doped fluorides and chlorides exhibited mid-infrared emissions at ~4500 nm at room temperature. The mid-infrared emission at 4500 nm, originating from the 4I9/2 -> 4I11/2 transition, showed long emission lifetime values of ~11.6 ms and ~3.2 ms for Er3+ doped CsCdCl3 and KPb2Cl5 crystals, respectively. In comparison, Er3+ doped and BaF2 and NaYF4 demonstrated rather short lifetimes in the microsecond range of ~47 us and ~205 us, respectively. Temperature dependent decay time measurements were performed for the 4I9/2 excited state for Er3+ doped BaF2, NaYF4, and CsCdCl3 crystals. We noticed that the emission lifetimes of Er3+:CsCdCl3 were nearly independent of the temperature, whereas significant emission quenching of 4I9/2 level was observed for both Er3+ doped fluoride crystals. The temperature dependence of the multiphonon relaxation rate for 4.5 um mid-IR emissions was determined for the studied Er3+ doped fluorides using the well-known energy-gap law. Using ~890 nm excitation, all studied Ho3+ doped fluorides and chlorides exhibited mid-infrared emissions at ~3900 nm originating from the 5I5 -> 5I6 transition. The longest emission lifetime of the 5I5 level was determined to be ~14.55 ms from the Ho3+:CsCdCl3 crystal. The room temperature stimulated emission cross-sections for the Er3+ 4I9/2 -> 4I11/2 and Ho3+ 5I5 -> 5I6 transitions were determined using the Füchtbauer-Landenburg equation. Among the studied crystals, Er3+ doped chlorides are more than two orders of magnitude better in terms of emission lifetimes and sigma-tau product than the fluoride crystals. 

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4. A highly stable and conductive cerium‐doped Li ₇ P ₃ S ₁₁ glass‐ceramic electrolyte for solid‐state lithium–sulfur batteries

   https://doi.org/10.1111/jace.19712  

   Mirtaleb, Amirhossein; Wang, Ruigang (June 2024, Journal of the American Ceramic Society)

   Abstract In this report, a facile wet chemical method using acetonitrile combined with thermal annealing was used to prepare Li₂S‐P₂S₅(LPS) based glass‐ceramic electrolytes with (1 wt%, 3 wt%, and 5 wt% Ce₂S₃) and without Ce₂S₃doping. The crystal structure, ionic conductivity, and chemical stability of Li₇P₃S₁₁glass‐ceramic electrolytes were examined at varying temperatures (250–350°C). The results indicated that the highest ionic conductivity of 3.15 × 10⁻⁴S cm⁻¹for pure Li₇P₃S₁₁was observed at a temperature of 325°C. By incorporating 1 wt% Ce₂S₃and subjecting it to a heat treatment at 250°C, the glass ceramic electrolyte attained a remarkable ionic conductivity of 7.7 × 10⁻⁴(S cm⁻¹) at 25°C. Furthermore, it exhibited a stable and extensive electrochemical potential range, reaching up to 5 volts when compared to the Li/Li⁺reference electrode. By tuning the glass transition and crystallization temperature, cerium doping seems to make Li₇P₃S₁₁more chemically stable, compared to its original 70Li₂S‐30P₂S₅counterpart. According to Raman and X‐ray photoelectron spectroscopy analyses, cerium doping inhibits the decomposition of highly conductive P₂S₇^4‐(pyro‐thiophosphate) to PS₄³⁻and P₂S₆⁴⁻. Doped LPS has a greater crystallinity and more uniform microstructure than pure LPS, according to XRD, Raman spectroscopy, and scanning electron microscopy analysis. Consequently, Li₇P_2.9Ce_0.1S₁₁electrolyte shows great potential as a solid‐state electrolyte for constructing high‐performance sulfide‐based all‐solid‐state batteries. 

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5. Materials development and mid-infrared emission properties of Dy-doped TlPb2Br5 and CsPbCl3

   U. Hommerich, D. Hart (January 2020, Proc. SPIE 11276, Optical Components and Materials XVII)

   We report on the materials development and infrared (IR) optical spectroscopy of Dy3+-doped into the ternary lead halides compounds TlPb2Br5 and CsPbCl3 for photonic applications. The investigated Dy-doped ternary lead halides were synthesized from purified starting materials followed by melt-growth using vertical Bridgman technique. Under optical pumping at 1.35 m (6H15/26H9/2+6F11/2), broad mid-IR emissions in the ~2.9 µm (6H13/26H15/2), ~4.3 µm (6H11/26H13/2), and ~5.4 µm (6H9/2 +6F11/2 6H15/2) regions were observed at room-temperature. Compared to Dy: TlPb2Br5, the mid-IR emission from Dy: CsPbCl3 was significantly weaker suggesting the existence of non-radiative losses. Temperature dependent lifetime studies and a Judd-Ofelt analysis were performed for Dy: TlPb2Br5. 

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