Aspects of lithium tri- and tetraborate synthesis in the subsolidus region

The present work is focused at studying the transformation patterns for the crystalline structure of phases formed during the synthesis of polycrystalline lithium tri- and tetraborate. In the field of lithium triborate (LiB₃O₅) and tetraborate (Li₂B₄O₇) of the Li₂O – B₂O₃ system, LiB₃O₅ and Li₂B₄O₇ polycrystalline powders were synthesised.

In terms of precursors, lithium carbonate (Li₂CO₃) and boric acid (H₃BO₃) were selected. Two synthesis methods were tested including precipitation from solution and solid-phase synthesis. As a result, the direct sintering of a mechanically-grinded stoichiometric precursor mixture is shown to be the optimal method for crystallising LiB₃O₅ and Li₂B₄O₇. The crystallisation patterns of lithium borates were studied in a temperature range of 500-850 °C with sampling carried out every 50 °C. Individual phase portraits were established presenting a set of process character-istics depending on the level of substance particle organisation and subsolidus crystallisation from the initial reagent mixture of lithium tri- and tetraborate at the phase, local and structural levels. In a lithium triborate stoichiometric mixture, the maximum conversion of crystalline phases is observed in the region of 500–600 °C, while, for lithium tetraborate, the temperature maximum is in the range of 600–700 °C. The sequence of phase transformations re-mains almost unchanged and occurs according to the following scheme: starting reagents > intermediate metastable phases > final borates. The local level of phase portraits characterises the interaction of coordination polyhedra forming the crystal lattice of the studied phases. Solid-phase synthesis of crystalline LiB₃O₅ from the Li₂CO₃ and H₃BO₃ takes place as a result of (BO₃)^3- → (B₃O₇)^5- transition with the (BO₃)^3- → (B₄O₉)^6- scheme realised in obtaining Li₂B₄O₇. At the crystal structure level, such transitions correspond to transformations of the monoclinic lattice of the Li₂CO₃ and H₃BO₃ primary phases into the LiB₃O₅ and Li₂B₄O₇ rhombic and tetragonal structure, respectively.

In this case, an intermediate step of this transformation consists in formation of the LiBO₂ trigonal chain metaborate and metastable Li₂B₈O₁₃.

1. Anjaiah J, Laxmikanth C, Veeraiah N, Kristaiah P. Luminescence properties of Pr3+ doped Li2O–MO– B2O3 glasses. Journal of Luminescence. 2015; 161:147–153. https://doi.org/10.1016/j.jlumin.2015.01.007

2. Pawar PP, Munishwar SR, Gedam RS. Intense white light luminescent Dy3+ doped lithium borate glasses for W-LED: A correlation between physical, thermal, structural and optical properties. Solid State Sciences. 2017;64:41–50. https://doi.org/10.1016/j.solidstatesciences.2016.12.009

3. Laorodphan N, Kidkhunthod P, Khajonrit J, Montreeuppathum A, Chanlek N, Pinitsoontorn S, et al. Effect of B2O3 content on structure-function of vanadium‑lithium-borate glasses probed by synchrotron-based XAS and vibrating sample magnetrometry technique. Journal of Non-Crystalline Solids. 2018; 497:56–62. https://doi.org/10.1016/j.jnoncrysol.2018.04.045

4. Saidu A, Wagiran H, Saeed MA, Obayes HK, Bala A, Usman F. Thermoluminescence response of rare earth activated zinc lithium borate glass. Radiation Physics and Chemistry. 2018;144:413–418. https://doi.org/10.1016/j.radphyschem.2017.10.004

5. Neumair SC, Vanicek S, Wurst K, Huppertz H, Kaindl R, Többens DM. High-pressure synthesis and crystal structure of the lithium borate HP-LiB3O5. Journal of Solid State Chemistry. 2011; Vol. 184(9):2490–2497. https://doi.org/10.1016/j.jssc.2011.07.011

6. Sanyal B, Goswami M, Shobha S, Prakasan V, Chawla SP, Krishnan M, et al. Synthesis and characterization of Dy3+ doped lithium borate glass for thermoluminescence dosimetry. Journal of Non-Crystalline Solids. 2017;475:184–189. https://doi.org/10.1016/j.jnoncrysol.2017.09.016

7. Ramteke DD, Ganvira VY, Munishwar SR, Gedam RS. Concentration Effect of Sm3+ Ions on Structural and Luminescence Properties of Lithium Borate Glasses. Physics Procedia. 2015;76:25–30. https://doi.org/10.1016/j.phpro.2015.10.005

8. Kindrat II, Padlyak BV, Drzewiecki A. Luminescence properties of the Sm-doped borate glass-es. Journal of Luminescence. 2015;166:264–275. https://doi.org/10.1016/j.jlumin.2015.05.051

9. Mhareb MHA, Hashim S, Ghoshal SK, Alajerami YSM, Bqoor MJ, Hamdan AI, et al. Effect of Dy2O3 impurities on the physical, optical and thermoluminescence properties of lithium borate glass. Journal of Luminescence. 2016;177:366–372. https://doi.org/10.1016/j.jlumin.2016.05.002

10. Danilyuk PS, Volovich PN, Rizak VM, Puga PP, Gomonai AI, Krasilinets VN. X-ray luminescence and spectroscopic characteristics of Er3+ ions in a glassy lithium tetraborate matrix. Optics and Spectroscopy. 2015;118(6):924–929. https://doi.org/10.1134/S0030400X15060089

11. Rimbach AC, Steudel F, Ahrens B, Schweizer S. Tb3+, Eu3+, and Dy3+ doped lithium borate and lithium aluminoborate glass: Glass properties and photoluminescence quantum efficiency. Journal of Non-Crystalline Solids. 2018;499:380–386. https://doi.org/10.1016/j.jnoncrysol.2018.07.029

12. Bødker MS, Mauro JC, Youngman RE, Smedskjaer MM. Statistical mechanical modeling of borate glass structure and topology: prediction of superstructural units and glass transition temperature. Journal of physical chemistry b: biophysical chemistry, biomaterials, liquids, and soft matter. 2019;123(5):1206–1213. https://doi.org/10.1021/acs.jpcb.8b11926

13. Rollet AP, Bouaziz R. The binary system: lithium oxide-boric anhydride. Comptes Rendus de l'Academie des Sciences. 1955;240(25):2417–2419.

14. Sastry BSR, Hummel FA. Studies in Lithium Oxide Systems: I, Li2O-B2O3. Journal of the American Ceramic Society. 1958;41(1):7–17. https://doi.org/10.1111/j.1151-2916.1958.tb13496.x

15. Meshalkin AB. Investigation of phase equilibria and assessment of thermodynamic properties of melts in binary borate systems. Teplofizika i aeromekhanika = Thermophysics and Aeromechanics. 2005;12(4):669–684. (In Russian)

16. Voron'ko YuK, Sobol' AA, Shukshin VE. Investigation of phase transformations in LiB3O5 and Li2B4O7 during heating and melting by Raman spectroscopy. Neorganicheskie materialy = Inorganic Materials. 2013;49(9):991–997. (In Russian) https://doi.org/10.7868/S0002337X13090200

17. Bazarova ZhG, Nepomnyashchikh AI, Ko-zlov AA, Bogdan-Kurilo VD, Bazarov BG, Subanakov AK, et al. Phase Equilibria in the System Li2O– MgO–B2O3. Russian Journal of Inorganic Chemistry. 2007;52(12):1971–1973. https://doi.org/10.1134/S003602360712025X

18. Depci T, Özbayoğlu G, Yilmaz A. The effect of different starting materials on the synthesis of lithium triborate. Physicochemical Problems of Mineral Processing. 2007;41:101–105.

19. Mikhailov MA, Mamontova SG, Zelentcov SZ, Demina TV, Belozerova OYu, Bogdanova LA. On the Coexistence of Chemically Similar Stable and Metastable Phases in the BeO–MgO–Al2O3– SiO2 System. Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques. 2018;12(4): 756–760. https://doi.org/10.1134/S1027451018040328

20. Gorelik VS, Vdovin AV, Moiseenko VN. Raman and hyperrayleigh scattering in lithium tetraborate crystals. Journal of Russian Laser Research. 2003;24(6):553–605. https://doi.org/10.1023/B:JORR.0000004168.99752.0e