Ionic Conduction Mechanism in 4CaO·P<SUB>2</SUB>O<SUB>5</SUB> Compound

Measurement of transference number of 4CaO·P2O5 showed that the transference number of calcium ion was unity at 1773 K and independent of the partial pressure of oxygen between 2.1×104 Pa and 5×10−1 Pa. The electric conductivity was independent of the partial pressure of oxygen between 1×105 and 1×10−5 Pa at 1373 and 1873 K, and was represented by log10σ(S·m−1)=7.19×10−3⁄T+0.925(±0.02). The electromotive force of the Galvanic cell of PO2, CaO(s), Pt/4CaO·P2O5/Pt, CaO·6Al2O3(s)+Al2O3(s), PO2 was independent of the partial pressure of oxygen, and its value was close those of the electromotive forces of the Galvanic cells using CaF2 and Caβ″–Al2O3 as the solid electrolyte in reference. Then, it was concluded that electric carrier in solid 4CaO·P2O5 was predominantly the calcium ion under the above conditions of temperature and oxygen partial pressure.