Liquid fragility maximum in lithium borate glass‐forming melts related to the local structure
- ISIS Neutron and Muon Source, Science and Technology Facilities Council Rutherford Appleton Laboratory Didcot UK
- X‐Ray Science Division, Advanced Photon Source Argonne National Laboratory Argonne Illinois USA
- Physics Department Coe College Cedar Rapids Iowa USA
- X‐Ray Science Division, Advanced Photon Source Argonne National Laboratory Argonne Illinois USA, Materials Development, Inc. Arlington Heights Chicago Illinois USA
Abstract The structure of liquid lithium pyroborate, Li 4 B 2 O 5 ( J = Li/B = 2), has been measured over a wide temperature range by high‐energy X‐ray diffraction, and compared to that of its glass and borate liquids of other compositions. The results indicate a gradual increase in tetrahedral boron fraction from 3(1)% to 6(1)% during cooling from T = 1271(15) to 721(8) K, consistent with the larger N 4 = 10(1)% found for the glass, and literature 11 B nuclear magnetic resonance measurements. van't Hoff analysis based on a simple boron isomerization reaction BØ 3 O 2 – ⇌ BØO 2 2– yields Δ H = 13(1) kJ mol –1 and Δ S = 40(1) J mol –1 K –1 for the boron coordination change from 4 to 3, which are, respectively, smaller and larger than found for singly charged isomers for J ≤ 1. With these, we extend our model for N 4 ( J , T ), nonbridging oxygen fraction f nbr ( J , T ), configurational heat capacity , and entropy S conf ( J , T ) contributions up to J = 3. A maximum is revealed in at J = 1, and shown semi‐quantitatively to lead to a corresponding maximum in fragility contribution, akin to that observed in the total fragilities by temperature‐modulated differential scanning calorimetry. Lithium is bound to 4.6(2) oxygen in the pyroborate liquid, with 2.7(1) bonds centered around 1.946(8) Å and 1.9(1) around 2.42(1) Å. In the glass, n LiO = 5.4(4), the increase being due to an increase in the number of short Li–O bonds.
- Research Organization:
- Argonne National Laboratory (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- National Science Foundation (NSF); National Aeronautics and Space Administration (NASA); USDOE Office of Science (SC)
- Grant/Contract Number:
- SBIR DE‐SC0015241; DE‐SC0018601; AC02-06CH11357; SC0015241; SC0018601; 80NSSC18K0059; DMR-1746230
- OSTI ID:
- 1886112
- Alternate ID(s):
- OSTI ID: 1902575; OSTI ID: 1970725
- Journal Information:
- International Journal of Applied Glass Science, Journal Name: International Journal of Applied Glass Science Vol. 14 Journal Issue: 1; ISSN 2041-1286
- Publisher:
- Wiley-BlackwellCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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