Hydroflux Synthesis and Crystal Structure of New Lanthanide Tungstate Oxyhydroxides

Single crystals of Na5Ln(OH)6WO4 where Ln = Er, Tm, and Yb were grown out of a NaOH hydroflux. The crystals were characterized by single crystal X-ray diffraction and were found to crystallize in the monoclinic space group I2/a. The lattice parameter ranges for the three structures are a = 11.2024(7) Å–11.2412(6) Å, b = 16.1850(10) Å–16.2220(10) Å, and c = 11.9913(7) Å–12.0323(7) Å while the β angle range is 101.999(2)°–102.025(2)°

Photoluminescent and Magnetic Properties of Lanthanide Containing Apatites: Na\u3csub\u3ex\u3c/sub\u3eLn\u3csub\u3e10–x\u3c/sub\u3e(SiO\u3csub\u3e4\u3c/sub\u3e)\u3csub\u3e6\u3c/sub\u3eO\u3csub\u3e2–y\u3c/sub\u3eF\u3csub\u3ey\u3c/sub\u3e, Ca\u3csub\u3ex\u3c/sub\u3eLn\u3csub\u3e10–x\u3c/sub\u3e(SiO\u3csub\u3e4\u3c/sub\u3e)\u3csub\u3e6\u3c/sub\u3eO\u3csub\u3e2–y\u3c/sub\u3eF\u3csub\u3ey\u3c/sub\u3e (Ln = Eu, Gd, and Sm), Gd\u3csub\u3e9.34\u3c/sub\u3e(SiO\u3csub\u3e4\u3c/sub\u3e)\u3csub\u3e6\u3c/sub\u3eO\u3csub\u3e2\u3c/sub\u3e, and K\u3csub\u3e1.32\u3c/sub\u3ePr\u3csub\u3e8.68\u3c/sub\u3e(SiO\u3csub\u3e4\u3c/sub\u3e)\u3csub\u3e6\u3c/sub\u3eO\u3csub\u3e1.36\u3c/sub\u3eF\u3csub\u3e0.64\u3c/sub\u3e

Single crystals of NaEu9(SiO4)6O2, Na1.5Eu8.5(SiO4)6OF, Na1.64Gd8.36(SiO4)6O0.72F1.28, Gd9.34(SiO4)6O2, Ca2.6Eu7.4(SiO4)6O1.4F0.6, Ca4.02Sm5.98(SiO4)6F2, and K1.32Pr8.68(SiO4)6O1.36F0.64 and powders of NaEu9(SiO4)6O2, Na1.5Eu8.5(SiO4)6OF, Eu9.34(SiO4)6O2, and Gd9.34(SiO4)6O2 were synthesized via flux growth in selected alkali-fluoride melts. All of the compounds adopt the apatite structure with space group P63/m. Luminescence and magnetic data were collected on NaEu9(SiO4)6O2, Na1.5Eu8.5(SiO4)6OF, Eu9.34(SiO4)6O2, and Gd9.34(SiO4)6O2. Luminescent data indicate that changing the cations and anions that surround the lanthanide site does not change the luminescent properties, making apatites versatile structures for optical materials

Observation of Intense X‑ray Scintillation in a Family of Mixed Anion Silicates, Cs₃RESi₄O₁₀F₂ (RE = Y, Eu–Lu), Obtained via an Enhanced Flux Crystal Growth Technique

A new family of mixed anion cesium rare earth silicates exhibiting intense scintillation in several ranges of the visible spectrum are reported. Cs₃RESi₄O₁₀F₂ (RE = Y, Eu–Lu) have been synthesized using an enhanced flux growth method for the targeted growth of mixed anion systems. This is the first example of this method being used for the growth of oxyhalides. The compounds crystallize in the triclinic space group <i>P</i>1̅ with the lattice parameters <i>a</i> = 7.0832(2) Å, <i>b</i> = 7.1346(2) Å, <i>c</i> = 16.2121(5) Å, α = 95.8090(10)°, β = 90.0580(10)°, γ = 119.7650(10)° for the Tb analogue. The structure consists of REO₆ and REO₂F₄ polyhedra connected by Si₄O₁₀ sheets with a previously unobserved silicate sheet topology that contains the uncommon cyclic Si₃O₉ trimers. The synthesis, structure, magnetic and optical properties are reported including, notably, intense X-ray scintillation in Cs₃TbSi₄O₁₀F₂

Integrating Archaeological Theory and Predictive Modeling: a Live Report from the Scene

Archaeological predictive modeling has been used successfully for over20 years as a decision-making tool in cultural resources management. Itsappreciation in academic circles however has been mixed because of its perceivedtheoretical poverty. In this paper, we discuss the issue of integrating currentarchaeological theoretical approaches and predictive modeling. We suggest amethodology for doing so based on cognitive archaeology, middle range theory,and paleoeconomic modeling. We also discuss the problems associated with testingpredictive models