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本文用X射线衍射(高温、室温)相热分析(DTA、DSC、TGA)等方法测定了Li_2SO_4-MgSO_4和Li_2SO_4-Li_4SiO_4体系相图,并研究了化合物的性能和晶体结构. Mg_4Li_2(SO_4)_5在840℃由包晶反应形成,它在105℃分解为Li_2SO_4为基的固溶体和MgSO_4.在105℃反应时,形成每摩尔的Mg_4Li_2(SO_4)_5吸热2.57kJ,反应激活能为173.5kJ/mol.Mg_4Li_2(SO_4)_5属正交晶系,在180℃的点阵常数α=8.577A,b=8.741A,c=11.918A,可能的空间群为.P222或Pmmm,Z=2. Li_(8-2x)(SiO_4)_(2-x)(SO_4)_x是在953℃由包晶反应形成的新相.随着温度的降低,相区扩大.在室温x=0.96—0.58.该相属正交晶系,空间群为.Pmmm,Z=2.晶体的点阵常数在x=0.8时有一最大值,α=5.002A,b=6.173A,c=10.608A.Li_(8-2x)(SiO_4)_(2-x)(SO_4)_x在空气中能吸收7.6wt％的水蒸气和其他气体.脱水温度高于350℃,水份的吸脱不改变晶体结构,与沸石分子筛具有相似性质,脱水激活能为171.5kJ/mol. 熔化后的Li_2SO_4-MgSO_4和Li_2SO_4-Li_4SiO_4试样以10℃/min速率降温,分别形成亚稳态共晶体系.
In this paper, the phase diagrams of Li_2SO_4-MgSO_4 and Li_2SO_4-Li_4SiO_4 system were measured by X-ray diffraction (high temperature, room temperature) phase analysis (DTA, DSC, TGA) and the properties and crystal structure of the compounds were also studied.Mg_4Li_2 (SO_4) _5 Formed by peritectic reaction at 840 ℃ and decomposed into Li_2SO_4-based solid solution and MgSO_4 at 105 ℃ .At a temperature of 105 ℃, an endothermic 2.57kJ / mol Mg_4Li_2 (SO_4) _5 was formed and the reaction activation energy was 173.5kJ / mol.Mg_4Li_2 (SO_4) _5 belongs to the orthorhombic system. The lattice constants α = 8.577A, b = 8.741A and c = 11.918A at 180 ℃. The possible space groups are P222 or Pmmm and Z = (8-2x) (SiO_4) _ (2-x) (SO_4) _x is a new phase formed by peritectic reaction at 953 ° C. As the temperature decreases, the phase region expands. At room temperature x = 0.96-0.58. The orthorhombic system belongs to the orthorhombic space group with a space group of .Pmmm and Z = 2. The lattice constant of the crystal has a maximum at x = 0.8, α = 5.002A, b = 6.173A, c = 10.608A.Li_ (8- 2x) (SiO_4) _ (2-x) (SO_4) _x can absorb 7.6wt% of water vapor and other gases in the air.The dehydration temperature is higher than 350 ℃, the adsorption of water does not change the crystal structure, Has similar properties, the dehydration activation energy is 171.5kJ / mol. The molten Li_2SO_4-MgSO _4 and Li_2SO_4-Li_4SiO_4 samples were cooled at a rate of 10 ℃ / min to form metastable eutectic systems respectively.