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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