New Li+ ion conductors in the system Li4SiO4−Li3AsO4
1982; Elsevier BV; Volume: 7; Issue: 1 Linguagem: Inglês
10.1016/0167-2738(82)90060-1
ISSN1872-7689
AutoresA. Khorassani, Anthony R. West,
Tópico(s)Chemical Synthesis and Characterization
ResumoIn the system Li4SiO4-Li3AsO4, Li4SiO4 forms a short range of solid solutions containing up to 14 to 20% Li3AsO 4, depending on temperature, and γ-Li3AsO4 forms a more extensive range of solid solutions containing up to ≈55% Li4SiO4. The Li4SiO4-Li3AsO4 phase diagram has been determined and is of binary eutectic character. The ac conductivity of polycrystalline samples was measured over the range 0 to at least 300°C for nine different compositions. The two solid solution series have much higher conductivity than the pure end-members; maximum conductivity was observed in the γ-Li3AsO4 solid solutions containing ≈40 to 55% Li4SiO4, with values of ≈2×10−6 Ω−1 cm−1 at 20°C rising to ≈0.02 Ω−1 cm−1 at 300°C. These values are comparable to those found in the system Li4SiO4-Li3PO4. The variation with composition of the Arrhenius prefactor and activation energy has been interpreted in terms of the mechanisms of conduction. Li3AsO4 is a poor conductor essentially because the number of mobile Li+ ions is very small. This number, and hence the conductivity, increases dramatically on forming solid solutions with Li4SiO4, by the creation of interstitial Li+ ions. At ≈40 to 55% Li4SiO4, the number of mobile Li+ ions appears to be optimised. An explanation for the change in activation energy of conduction at ≈290°C in Li4SiO4 and at higher temperatures in Li4SiO4 solid solutions is given in terms of order-disorder of the Li+ ions.
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