Small polaron conduction in V2O5P2O5 glasses
1973; Elsevier BV; Volume: 11; Issue: 5 Linguagem: Inglês
10.1016/0022-3093(73)90089-6
ISSN1873-4812
Autores Tópico(s)Solid-state spectroscopy and crystallography
ResumoDc conductivity measurements have been made between 90 and 520 K on three bulk samples of V2O5P2O5 glass. Heat treatment is found to result in a reduction of the activation energy at a given temperature and this is most noticeable at low temperatures. The behaviour at low temperatures can be described using Mott's variable range hopping arguments, and at high temperatures by non-adiabatic small polaron hopping between nearest neighbours. At intermediate temperatures a simple model is used in which excitations by optical and acoustic phonons are considered to make independent contributions to the jump frequency. Mott's theory is extended to the polaron case for T>14⊖ and is shown to be in good agreement with results. Values for rp(∼2.8 Å) the polaron radius and α(∼3.5 Å−1) the electron decay constant are shown to be consistent with the model for small polarons. A method is suggested for obtaining α and N(EF) from the ac conductivity and the slope of 1nσ versus 1T14 at low temperatures. Values of N(E) are obtained which correlate with those obtained by the previous analysis. This implies that the disorder energy separating adjacent sites Δ0 is large (∼0.4 eV) in these materials.
Referência(s)