ELECTROCHEMICAL STUDY OF THE CROSS EFFECT BETWEEN ION AND ELECTRON FLOWS IN SEMICONDUCTING COO

According to the linear transport theory, the mobile cation flux, J1, in an electronic conductor oxide, e.g., Co1-deltaO, is given as J1 = -L11 DEL(eta1) - L12 DEL(eta2), L(ik) (i,k = 1,2) being the transport coefficient and DEL(etak) the electrochemical potential gradient of charge carriers of type k (1 = Co2+; 2 = electron). It has, however, been normally presumed that L12 = 0 without experimental verification. By an electrochemical means we have measured the ''charge of transport'' of the cation, a1* (= L12/L11), in the ranges of temperature and oxygen partial pressure, 900 less-than-or-equal-to T/degrees-C less-than-or-equal-to 1030 and 5.8 x 10(-4) < P(o2)/atm less-than-or-equal-to 0.21, respectively, and found, contrary to the normal presumption, that a1* takes a value in a range of 0.7 to 1.6. Furthermore, it tends to increase with decreasing temperature and increasing oxygen partial pressure. The principle and details of the electrochemical experiment employed are given and the compilation is made of all the data on a1* of CoO which have been made available via various means up until now.