Conference article

In the scope of this work; (Bi₂O₃)1-x-y(Dy₂O₃)_x(Ho₂O₃)y ternary system (x=1;3;5;7;9;11 mol % and y=11;9;7;5;3;1 mol %; dopant concentrations) sample materials were developed using solid state reaction method sintering each of them at 650; 700; 750; 800 °C for 48 hours. Structural; electrical and thermal properties of these samples which are candidate of electrolyte for solid oxide fuel cells (SOFCs) have been evaluated by means of XRD; four-probe method; and TGA / DTA. XRD measurements showed that except the samples annealed at 650 oC; all the other samples have stabilized d- Bi₂O₃ phase. It was seen that duration of sintering time and temperature was rather effective on the formation of the stabilized sample materials and their other properties; such as electrical and structural properties. It was seen that the electrical conductivities of all the examples developed sintering at 700; 750 and 800 °C for 48 hours increases with the increasing temperature having numerical values varying in the range of 7;65x10^-2 O.cm^-1 - 6;11x10^-1 O.cm^-1. Activation energy of the sample A6 was calculated and it was found 0.97 eV. On the other hand; the main purpose of this study is to find an electrolyte which does not have any degradation in its properties with time; this maybe caused either interaction between the different electrochemical cell materials or by instability of the ionic conductor under operation conditions. During the heating/cooling process; the four-point probe conductivity measurements have been performed. The hysteresis curve was obtained for this sample due to time interval difference of heating/cooling processes. It was observed that there is no gradation in the structure of the sample.

Electrolyte; Solid state reaction; Fuel cell; Electrical conductivity; XRD; Four- probe point method