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1. Stability of the Y ₂ O ₃ –SiO ₂ system in high‐temperature, high‐velocity water vapor

   https://doi.org/10.1111/jace.16915  

   Parker, Cory G; Opila, Elizabeth J (April 2020, Journal of the American Ceramic Society)

   Abstract High‐temperature, high‐velocity water vapor (steam‐jet) exposures were conducted on Y₂O₃, Y₂SiO₅, Y₂Si₂O₇, and SiO₂for 60 hours at 1400°C. Volatility of Y₂O₃was not observed. Phase‐pure Y₂SiO₅exhibited SiO₂loss forming Y₂O₃and porosity. A mixed porous and dense Y₂SiO₅layer formed on the surface of Y₂Si₂O₇due to SiO₂depletion. The mechanisms and kinetics of the reaction between SiO₂and H₂O(g) to form Si(OH)₄(g) from Y₂SiO₅, Y₂Si₂O₇, and SiO₂are discussed. 

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2. The High-Temperature Polymorph of LiBF ₄

   https://doi.org/10.1021/acs.jpclett.3c02961  

   Sonnenberg, Laura A.; Chandra Paul, Shujit; Wunder, Stephanie L.; Zdilla, Michael J. (January 2024, The Journal of Physical Chemistry Letters)

   The single-crystal-to-single-crystal phase transition is determined using X-ray crystallography on LiBF4, resolving a longstanding ambiguity in the existence of a high-temperature polymorph of LiBF4. LiBF4 possesses an endothermic phase change at 28.2 °C with ΔH = 1180 J mol-1 and ΔS = 3.92 J mol-1K-1 based on DSC. Single-crystal X-ray diffraction shows that the low temperature phase collected at 200K is a twinned trigonal P system with a twin law indicating reflection through the 110 plane. The same crystal collected above the phase transition temperature at 313 K is a C-centered orthorhombic system describable as the superposition of the two low-temperature twin geometries undergoing interconversion. The geome-tries of the high- and low-temperature phases are consistent with the calorimetry experiments, and with previous NMR find-ings indicating BF4 geometric reorientations above 300 K. 

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3. High pressure high temperature devitrification of Fe ₇₈ B ₁₃ Si ₉ metallic glass with simultaneous x-ray structural characterization

   https://doi.org/10.1063/1.5024941  

   Stemshorn, Andrew K.; Vohra, Yogesh K.; Smith, Spencer J. (June 2018, Journal of Applied Physics)
4. Tetragonal Kondo Insulator EuCd ₂ Sb ₂ Discovered via High Pressure High Temperature Synthesis

   https://doi.org/10.1002/adfm.202303612  

   Jimenez, Jose L.; Melnick, Corey; Koirala, Krishna Prasad; Adler, Ran; Wang, Fei; Berrada, Meryem; Chen, Bin; Wang, Le; Walker, David; Kotliar, Gabriel; et al (July 2023, Advanced Functional Materials)

   Abstract Magnetic and electronic properties of quantum materials heavily rely on the crystal structure even in the same chemical compositions. In this study, it is demonstrated that a layered tetragonal EuCd 2 Sb 2 structure can be obtained by treating bulk trigonal EuCd 2 Sb 2 under high pressure (6 GPa) and high temperature (600 °C). Magnetization measurements of the newly formed layered tetragonal EuCd 2 Sb 2 confirm an antiferromagnetic ordering with Neel temperature ( T N ) around 16 K, which is significantly higher than that ( T N ≈ 7 K) of trigonal EuCd 2 Sb 2 , consistent with heat capacity measurements. Moreover, bad metal behavior is observed in the temperature dependence of the electrical resistivity and the resistivity shows a dramatic increase around the Neel temperature. Electronic structure calculations with local density approximation dynamic mean–field theory (LDA+DMFT) show that this material is strongly correlated with well‐formed large magnetic moments, due to Hund's coupling, which is known to dramatically suppress the Kondo scale. 

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5. Variable thermochemical stability of RE ₂ Si ₂ O ₇ (RE = Sc, Nd, Er, Yb, or Lu) in high‐temperature high‐velocity steam

   https://doi.org/10.1111/jace.18120  

   Ridley, Mackenzie; Opila, Elizabeth (September 2021, Journal of the American Ceramic Society)

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