Studies on Li2SO4-MgSO4 and Li2SO4-Li4SiO4 systems
Studies on Li2SO4-MgSO4 and Li2SO4-Li4SiO4 systems作者机构：Institute of Physics Academia Sinica. Beijing
出 版 物：《Chinese Journal of Chemistry》 (中国化学(英文版))
年 卷 期：1986年第4卷第2期
页 面：123-132页
主 题：Li MgS Studies on Li2SO4-MgSO4 and Li2SO4-Li4SiO4 systems SiO SO
摘 要：The phase equilibria as well as the properties and crystal structures of the compoundsformed in both Li2SO4-MgSO4and Li2SO4-Li4SiO4systems have been studied by means of x-raydiffraction technique（at high and room temperatures）as well as by the thermal analyses（DTA, DSC,TGA, etc.）. In Li2SO4-MgSO4system there exists a compound Mg4Li2（SO4）5formed by peritectic reactionat 840℃ and decomposed at 105℃ into the Li2SO4-base solid solution and MgSO4Mg4Li2（SO4）5and Li2SO4-base solid solution conduct an eutectic reaction at 668℃ with the composition of eutecticpoint lying in 22 mol％MgSO4. The solubility of MgSO4in Li2SO4is a little smaller than 10 mol%while at the same time the Li2SO4phase transition temperature decreases from 574 to 560℃. Onthe other hand, no noticeable solid solubility of Li2SO4in MgSO4has been observed. The reaction4 MgSO4+Li2SO4Mg4Li2（SO4）5is an endothermal one and its heat of formation is 2.57 kJ/mol. The activation energy of the reaction calculated by thermal peak displacement method at variousheating rates is 173.5 kJ/mol （1.80 ev）. The crystal Mg4Li2（SO4）5belongs to orthorhombic systemwith lattice parameters at 180℃: a=8.577, b=8.741. c=11.918 . The space group seems to beeither P222 or P mmm. Assuming that there are two formula units in a unit cell, the density calculatedis then 2.20 g/cm3very close to that of Li2SO4or MgSO4. Meanwhile, in Li2SO4-Li4SiO4system a new phase Li8-2x（SiO4）2-x（SO4）xis formed by peri-tectic reaction at 953℃ with a range of composition x=0.96-0.58. The crystal belongs to ortho-rhombic system with lattice parameters at x=0.8: a=5.002. b=6.173 and c=10.608 . The densityobserved is 2.31 g/cm3and there are 2 formula units in an unit cell. It is shown from the measure-ments of piezoelectric and laser SHG coefficients of the crystal that the crystal posseses a symmetricalcenter with the space group belonging to P mmm. The lattice parameter c has a maximum at x=*** the air Li8-2x（SiO4）(2-x)（SO4）xcan absorb 7.6 wt% water vapour a
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