OXYGEN IONIC TRANSPORT IN BI2O3-BASED OXIDES - THE SOLID-SOLUTIONS BI2O3-NB2O5

The minimum concentration of niobium to stabilize the fluorite-type f. c.c. phase in the Bi2O3Nb2O5 oxide system at temperatures below 996 K was ascertained to be about 10 mol%. Thermal expansion, electrical con ductivity and crystal lattice parameters of the Bi(Nb)O1.5+delta solid solutions decrease with increasing niobium content. Thermal expansion coefficients were calculated from the dilatometric data to be (10.3-1 4.5) x 10(-6) K-1 at temperatures in the range 300-700 K and (17.5-26. 0) x 10(-6) K-1 at 700-1100 K. The conductivity of the Bi1-xNbxO1.5+de lta ceramics is predominantly ionic. The p-type electronic transferenc e numbers of the Bi(Nb)O1.5+delta solid solutions in air were determin ed to be less than 0.1. Annealing at temperatures below 900 K results in a sharp decrease in conductivity of the Bi1-xNbxO1.5+delta ceramics .