Barium iron vanadate glass, e.g., 20BaO‧10Fe₂O₃‧ 70V₂O₅ (in mol %), and its analogs show high electrical conductivity amounting to the order of 10^-1 Scm^-1 [1-4]. This is brought about by the isothermal annealing for only several ten minutes at a given temperature higher than its glass transition temperature or crystallization temperature. The electrical conductivity are tunable from the order of 10^-6 to 10^-1 Scm^-1 by changing the condition of isothermal annealing. The marked increase in the electrical conductivity was attributed to the structural relaxation of the “3D-network” which was preferable for the small polaron hopping from V^IV to V^V. Substitution of Cu^I (3d¹⁰), Zn^II (3d¹⁰) and Cu^II (3d⁹) for Fe^III (3d⁵) caused a further increase in the electrical conductivity [2-4], e.g., 20BaO‧5Cu₂O‧5Fe₂O₃‧70V₂O₅ glass annealed at 450 °C for 30 min showed an increase of the electrical conductivity from 5.1×10^–6 Scm^–1 to 2.0×10^–1 Scm^–1, which was one order of magnitude larger than that of non-substituted vanadate glass (3.4×10^–2 Scm^–1) [2-4].

In this study, we investigated the substitutional effect of Sn^IV (4d¹⁰) and Sn^II (5s²) on the structure and the electrical conductivity of barium iron vanadate glass annealed at 500℃ for 0 - 300 min. The electrical conductivity of the annealed vanadate glass containing SnO (20BaO‧5Fe₂O₃‧5SnO‧70V₂O₅) was three orders of magnitude smaller than that of the conventional conductive vanadate glass (20BaO‧ 10Fe₂O₃‧70V₂O₅). Figure shows RT-Mössbauer spectrum of conductive vanadate glasses annealed at 500℃ for 60 min. The quadrupole splitting (Δ) of Fe^III increase from 0.57 to 0.66 mms⁻¹ as the composition of SnO increase, which reflected a decreased symmetry or an increased distortion of FeO₄ and VO₄tetrahedra [2-4]. Such a local distortion of the network should decrease the carrier mobility, and be contributed to the lower conductivity.

References:

1) Fukuda, A. Ikeda and T. Nishida, Solid State Phenom., 90/91, 215-220 (2003).

2) Nishida, S. Kubuki, K. Matsuda and Y. Otsuka, Croat. Chem. Acta 88(4) 427-435 (2015).

3) K. Matsuda, S. Kubuki and T. Nishida, AIP Conf. Proc. (msms2014), 1622, 3-7 (2014).

4) T. Nishida, Y. Izutsu, M. Fujimura, K. Osouda, Y. Otsuka, S. Kubuki and N. Oka, Pure and Appl. Chem. (2017). [DOI: https://doi.org/10.1515/pac-2016-0916]