Viscosity and IR investigations in the Li2O---B2O3 system |
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Authors: | Hanbin Liu Guangqiu Shen Xiaoqing Wang Jingzhi Wei Dezhong Shen |
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Institution: | b Department of Chemistry, Tsinghua University, Beijing 100084, China a Beijing Institute of Synthetic Crystals, Beijing 100018, China |
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Abstract: | The high viscosity in melts of the Li2O---B2O3 system makes it very difficult to grow large crystals of lithium triborate. The viscosity and IR characteristics of molten li2O---B2O3 system are reported in this paper. When the temperature increases the viscosity of li2O---B2O3 system decreases and follows an Arrhenius-type relationship. With an increasing 13203 ratio in Li2O---B2O3 melts, the viscosity rises gradually to a maximum with a composition Li2O: 3.513203 then it falls rapidly. In order to find active agents to reduce the viscosity, Na2O, NaCl, LiF, P205, M003, W03 etc oxides were added to Li2O---B2O3 samples respectively and investigated using the orthogonal method. The experimental results show that the addition of acidic oxides can significantly decrease the viscosity in the Li2O---B2O3 system. For Li2O: 4.513203, an ideal additive agent is 20wt% Li2O:: 2MoO3. Near the composition for crystal growth, the percentage reduction of viscosity is 62.2%. The IR spectra of Li2O---B2O3 system revealed that the BO4−/NO3− ratio is reduced in the melt using Li2O: 2MoO3 as an additive. It is proposed that the M003 reduced the concentration of bridging oxygen atoms of BO4−. The change of structure explains the decline in the viscosity. In the crystal structures of lithium triborate, the matrix spaces are so small that larger other cations than Li+ are very difficult to enter the crystal matrix. So the use of additive agents to reduce the viscosity is a possible method if no new phase appears. |
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Keywords: | Li2O---B2O3 system viscosity IR spectra adductive agents |
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