Diagram Example : Fixation of Chemical Potential 3b

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The chemical potential diagram for the La-Mn-Zr-O system at 1273 K.

1. Diagram : The three dimensional diagram in the μ(La)-μ(Mn)-μ(Zr) plot.
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2. Description of Diagram Example : Fixation of Chemical Potential (3b)
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   • Comparison is made with (2b) where the chemical potential diagram for La-Mn-O system is given.
     
   • The stability region of La₂O₃ is replaced by that of La₂Zr₂O₇. This corresponds to the following reaction;
     

     La₂O₃ + 2ZrO₂ = La₂Zr₂O₇
     

   • Since the activity of ZrO₂ is equal to unity in the present diagram, the activity of La₂O₃ is fixed at a certain value in the La2Zr2O7 stability region. This change in the activity of La₂O₃ compared with (2b) make a shift of the location of the La₂O₃ plane to the La₂Zr₂O₇. As a result, the three phase point of MnO, LaMnO₃ and La₂Zr₂O₇ is located at a point which has a lower La activity value. This point can be written down as
     
     LaMnO₃ + ZrO₂ = 0.5 La₂Zr₂O₇ + MnO + 1/4 O₂(g)
     
   • Among the five chemical species involved in the reaction, three are shown as the stable phase plane, one is given as a species whose chemical potential is fixed and one is given as one of species which are used as axes of diagram.
     
   • The three phase point of MnO₂, LaMnO₃ and La₂Zr₂O₇ shows the following reaction;
     
     LaMnO₃ + ZrO₂ + 1/4 O₂(g) = 0.5 La₂Zr₂O₇ + MnO₂
     
   
   
3. Detailed procedure for reproducing Diagram Example
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   1. [System] MALT

      Search Compounds

   Selection of <La,Mn,Zr,O> system

   2. Project > Chemical System

   3. [Chemical System] dialog
      
      • [Select Compound] page
        
        Selection by Default
        
        x Condensed phases
        o Respective Gaseous Species
        o Gaseous mixture
        

   4. Project > Specify Diagram

   5. [Diagram Specification]Dialog Main part
      
      • (1) Dimension SelectionPage
        
        Temperature
        
        x Fixed at 1273 K
        o Not Fixed
        
        Pressure
        
        x Fixed at 1 atm
        o Not Fixed
        
      • (2) Fixation page
        
        Add
        
        [Select Fixation] dialog
        
        Select "ZrO2" phase
        
        [Coefficient] dialog
        
        Select ReEnter 1.0
        
      • (3) Diagram Selection page
        
        3D surface
        Coordinates
        
        (La)
        (Mn)
        (O)
        

   6. Run > Calculation

   7. Diagram > Color Details

   8. [Diagram Action Form]
      
      (3) Polygon Color
      
      (1)Tricolors based on the Coordinates
      
      X-Axis red
      Y-Axis yellow
      Z-axis Blue
      
      (3){Colors based on Given Colors} Page
      
      1) Select first ?Current TriColor? button
      
      29 Then, Select ?LaMnO3? phase and
      Change Color to red