1. Exploring the Effect of V 2 O 5 and Nb 2 O 5 Content on the Structural, Thermal, and Electrical Characteristics of Sodium Phosphate Glasses and Glass–Ceramics.
- Author
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Marijan, Sara, Klaser, Teodoro, Mirosavljević, Marija, Mošner, Petr, Koudelka, Ladislav, Skoko, Željko, Pisk, Jana, and Pavić, Luka
- Subjects
PHOSPHATE glass ,GLASS-ceramics ,SODIUM phosphates ,TRANSITION metal ions ,ALKALI metal ions ,TRANSITION metal oxides ,IONIC conductivity - Abstract
Na-V-P-Nb-based materials have gained substantial recognition as cathode materials in high-rate sodium-ion batteries due to their unique properties and compositions, comprising both alkali and transition metal ions, which allow them to exhibit a mixed ionic–polaronic conduction mechanism. In this study, the impact of introducing two transition metal oxides, V
2 O5 and Nb2 O5 , on the thermal, (micro)structural, and electrical properties of the 35Na2 O-25V2 O5 -(40 − x)P2 O5 − xNb2 O5 system is examined. The starting glass shows the highest values of DC conductivity, σDC , reaching 1.45 × 10−8 Ω−1 cm−1 at 303 K, along with a glass transition temperature, Tg , of 371 °C. The incorporation of Nb2 O5 influences both σDC and Tg , resulting in non-linear trends, with the lowest values observed for the glass with x = 20 mol%. Electron paramagnetic resonance measurements and vibrational spectroscopy results suggest that the observed non-monotonic trend in σDC arises from a diminishing contribution of polaronic conductivity due to the decrease in the relative number of V4+ ions and the introduction of Nb2 O5 , which disrupts the predominantly mixed vanadate–phosphate network within the starting glasses, consequently impeding polaronic transport. The mechanism of electrical transport is investigated using the model-free Summerfield scaling procedure, revealing the presence of mixed ionic–polaronic conductivity in glasses where x < 10 mol%, whereas for x ≥ 10 mol%, the ionic conductivity mechanism becomes prominent. To assess the impact of the V2 O5 content on the electrical transport mechanism, a comparative analysis of two analogue series with varying V2 O5 content (10 and 25 mol%) is conducted to evaluate the extent of its polaronic contribution. [ABSTRACT FROM AUTHOR]- Published
- 2024
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