DESIGN OF SOLID ELECTROLYTES FOR USE WITH DISSIMILAR GAS ELECTRODES

The design of a solid electrolyte that permits the use of dissimilar g as electrodes in an electrochemical cell is presented. It consists of a functionally gradient material with spatial variation in composition . The activity of the conducting ion is fixed at each electrode using different gas species. The system chosen for demonstrating the concept consists of a solid solution between K2CO3 and K2SO4. The composition of the solid solution varies from pure K2CO3 in contact with a CO2 O-2 gas mixture at one electrode to pure K2SO4 exposed to a mixture of SO3 + SO2 + O-2 at the other. Two types of composition profiles are s tudied, one with monotonic variation in composition and the other with extrema. The e.m.f. of the cells is studied as a function of temperat ure and composition of the gas mixture at each electrode. The results indicate that the e.m.f. is determined primarily by the difference in the chemical potential of potassium at the two electrodes. The diffusi on potential caused by ionic concentration gradients in the electrolyt e appears to be negligible when the corresponding ionic transport numb ers are insignificant. Studies on the response characteristics of the cell based on the gradient electrolyte indicate that the nature of the variation in composition of the electrolyte has only a minor effect o n the time evolution of e.m.f. The gradient solid electrolytes have po tential application in multielement galvanic sensors at high temperatu res.