ESTIMATION OF THE FREE-CHARGE-CARRIER CONCENTRATION IN FAST-ION CONDUCTING NA2S-B2S3 GLASSES FROM AN ANALYSIS OF THE FREQUENCY-DEPENDENT CONDUCTIVITY

ac and dc conductivities of fast-ion conducting xNa(2)S+(1-x)B2S3 glas ses in the composition range 0.001 less than or equal to x less than o r equal to 0.1 were analyzed using the Almond-West formula sigma(nu)=s igma(dc)[1+(nu/nu(H))(alpha)]. The hopping frequency for free charge c arriers nu(H), the dc conductivity sigma(dc), and their respective act ivation energies were determined. The concentration of free charge ear ners evaluated from the conductivities and estimated mobilities is in good agreement with the overall content of sodium cations in the, glas ses and it is proposed that this supports the concept of a strong and not weak electrolyte model for these fast-ion conducting glasses.