Gibbs energy of formation of Cu_2R_2O_5 (R = Dy, Ho, Er, Yb) from component oxides employing solid oxide electrochemical cells

摘要

High temperature phase relations in the Cu-R-O (R = Dy, Ho, Er, Yb) ternary systems suggest that there exists only one ternary oxide, Cu_2R_2O_5(R = Dy, Ho, Er, Yb). One of the three phase fields in these systems which is of interest consists of Cu_2O + R_2O_3 + Cu_2R_2O_5. Chemical potential of oxygen for the co-existence of this three phase assemblage is measured between 1050-1325 K employing the solid-state electrochemical cell, (-)Pt/Cu_2O + R_2O_3 + Cu_2R_2O_5//(CaO)ZrO_2//O_2(P = 0.0212 MPa)/Pt( + ) Gibbs energy of formation of Cu_2R_2O_5 from component oxides is obtained by combining the measured oxygen potential for Cu_2O + R_2O_3 + Cu_2R_2O_5 three phase equilibrium and Cu_2O + CuO from literature. Based on the present results, Gibbs energy of formation of Cu_2Tb_2O_5, Cu_2Tm_2O_5, Cu_2Tm_2O_5 and Cu_2Lu_2O_5 has been estimated.