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运用热力学研究了氧化物固溶体相变消除问题。回顾近50年ZrO_2及SiO_2相变消失原因,其中对ZrO_2相变消失是由于固溶体的形成一节各家意见分歧甚大。推导了热力学公式以求固溶体相变消除的条件。这一公式为x_h(G_l~0—G_h~0)>(ΔG_(mh)-ΔG_(ml)或x_h(G_h~0-G_l~0)>(ΔG_(ml)-ΔG_(mh))式中x_h为高温型固溶体内溶剂mol% G_l~0为纯高温型溶剂在标准状态下自由能G_h~0为纯低温型溶剂在标准状态下自由能ΔG_(mh)为高温型同溶体生成时的混合自由能ΔG_(ml)为低温型固溶体生成时的混合自由能只有当G_l~0与G_h~0差额很大时,这一差额才可大于ΔG_(ml)与ΔG_(mh)的差额,从而使ΔG>0相变消失。但是由于高温型、低温型氧化物的化学键与配位数相同,它们的G_l~0与G_h~0差额很小,生成固溶体时,相变不能消除。
The problem of phase transformation of oxide solid solution was studied by using thermodynamics. Reviewing the causes of the disappearance of ZrO_2 and SiO_2 phase transformations in the recent 50 years, in which the disappearance of ZrO_2 phase transformation is due to the disagreement among various opinions on the formation of solid solution. The thermodynamic formula was deduced to eliminate the solid solution transformation. The formula is as follows: x_h (G_l - 0 - G_h - 0)> (ΔG_ (mh) - ΔG_ (ml) or x_h (G_h - 0_G_l_0)> (ΔG_ (ml) - ΔG_ (mh)) x_h is the solvent in high temperature type solid solution mol% G_l ~ 0 is pure high temperature type solvent Free energy in standard state G_h ~ 0 is pure low temperature type solvent In the standard state free energy ΔG_ (mh) The free energy ΔG_ (ml) is the free energy of mixing in the formation of low-temperature solid solution. Only when the difference between G_l ~ 0 and G_h ~ 0 is large, the difference can be greater than the difference between ΔG_ (ml) and ΔG_ (mh) However, due to the same chemical bond and coordination number of the high-temperature type and the low-temperature type oxide, the difference between G_l ~ 0 and G_h ~ 0 is very small, and the phase transition can not be eliminated when the solid solution is formed.