Combined Use of Oxide and Fluoride Solid Electrolytes for the Measurement of Gibbs Energy of Formation of Ternary Oxides : System Bi-Ca-O

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Phase equilibrium studies of the ternary system Bi–Ca–O at 1000 K and ambient pressure indicate that all the ternary oxides lie along the pseudo-binary line Bi<SUB>2</SUB>O<SUB>3</SUB>–CaO. Four ternary oxides, Bi<SUB>2</SUB>Ca<SUB>2</SUB>O<SUB>5</SUB>, Bi<SUB>6</SUB>Ca<SUB>4</SUB>O<SUB>13</SUB>, Bi<SUB>2</SUB>CaO<SUB>4</SUB> and Bi<SUB>14</SUB>Ca<SUB>5</SUB>O<SUB>26</SUB> and two phases of variable composition (δ and β) are identified. The chemical potential of CaO in two-phase fields of the pseudo-binary Bi<SUB>2</SUB>O<SUB>3</SUB>–CaO is determined as a function of temperature using solid state cells based on single crystal CaF<SUB>2</SUB> as the electrolyte. The chemical potential of Bi<SUB>2</SUB>O<SUB>3</SUB> in the two-phase fields is measured using cells incorporating (Y<SUB>2</SUB>O<SUB>3</SUB>)ZrO<SUB>2</SUB> as the solid electrolyte. The standard Gibbs free energy of formation of each ternary oxide from the binary oxides is calculated independently from the chemical potentials of CaO and Bi<SUB>2</SUB>O<SUB>3</SUB> in two-phase fields on either side of the compound composition. The independent assessments agree closely; the maximum difference in the value of Δ<I>G</I><SUB>f</SUB><SUP>0</SUP>(Bi<SUB>2<I>m</I></SUB>Ca<I><SUB>n</SUB></I>O<SUB>3<I>m</I>+<I>n</I></SUB>)/(<I>m</I>+<I>n</I>) is 170 J/mol of the component binary oxides. The results are discussed in the light of the phase diagram and compared with calorimetric and free energy measurements reported in the literature. The combined use of emf data from cells incorporating fluoride and oxide electrolytes enhances the reliability of derived data. Free energies of formation of ternary oxides from component binary oxides are given by the following equations:<BR>Bi<SUB>2</SUB>Ca<SUB>2</SUB>O<SUB>5</SUB>: Δ<I>G</I><SUP>0</SUP><SUB>f,ox</SUB>(J/mol)=−43800+5.79<I>T</I>(±900)<BR>Bi<SUB>6</SUB>Ca<SUB>4</SUB>O<SUB>13</SUB>: Δ<I>G</I><SUP>0</SUP><SUB>f,ox</SUB>(J/mol)=−109800+7.04<I>T</I>(±2300)<BR>Bi<SUB>2</SUB>CaO<SUB>4</SUB>: Δ<I>G</I><SUP>0</SUP><SUB>f,ox</SUB>(J/mol)=−31910+2.31<I>T</I>(±650)<BR>Bi<SUB>14</SUB>Ca<SUB>5</SUB>O<SUB>26</SUB>: Δ<I>G</I><SUP>0</SUP><SUB>f,ox</SUB>(J/mol)=−184560+12.76<I>T</I>(±4320)<BR>Bi<SUB>1.4</SUB>Ca<SUB>0.3</SUB>O<SUB>2.4</SUB> (β): Δ<I>G</I><SUP>0</SUP><SUB>f,ox</SUB>(J/mol)=−12290(±300) at 900 K<BR>Bi<SUB>1.56</SUB>Ca<SUB>0.22</SUB>O<SUB>2.56</SUB> (β): Δ<I>G</I><SUP>0</SUP><SUB>f,ox</SUB>(J/mol)=−9890(±180) at 900 K

収録刊行物

  • Materials transactions, JIM  

    Materials transactions, JIM 38(5), 427-436, 1997-05 

    The Japan Institute of Metals

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各種コード

  • NII論文ID(NAID)
    10002452568
  • NII書誌ID(NCID)
    AA10699969
  • 本文言語コード
    ENG
  • 資料種別
    ART
  • ISSN
    09161821
  • NDL 記事登録ID
    4231131
  • NDL 雑誌分類
    ZP41(科学技術--金属工学・鉱山工学)
  • NDL 請求記号
    Z53-J286
  • データ提供元
    CJP書誌  NDL  J-STAGE 
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