DETERMINATION OF THE HOLE CONDUCTIVITY OF SODIUM-BETA-ALUMINA BY POTENTIOMETRIC MEASUREMENTS

摘要

The p-electron conduction parameter a of Na-(β+β")-A1_2O_3 is determined by quantitatively evaluating the isothermal voltage response of the cell: Au | O_2, CO_2, Na_2CO_3| Na-(β+β")-A1_2O_3| NiO, FeO (glass) | FeNi48| Au to successive variations of the sodium activity of the measuring electrode by changing the composition of the CO_2+O_2 gas mixture. The findings reveal that the p-type electronic conductivity of the electrolyte may remarkably affect the performance of a potentiometric solid state CO_2 sensor. Within the temperature interval under investigation (320℃≤T≤ s 620 ℃) the results on a are in reasonably good agreement with data known from previous measurements. They give evidence that a is not necessarily a constant but may adapt to the sodium activity in the surroundings of the solid electrolyte.