Exploring the Effect of V2O5 and Nb2O5 Content on the Structural, Thermal, and Electrical Characteristics of Sodium Phosphate Glasses and Glass-Ceramics

Marijan, Sara; Klaser, Teodoro; Mirosavljević, Marija; Mošner, Petr; Koudelka, Ladislav; Skoko, Željko; Pisk, Jana; Pavić, Luka (2024) Exploring the Effect of V2O5 and Nb2O5 Content on the Structural, Thermal, and Electrical Characteristics of Sodium Phosphate Glasses and Glass-Ceramics. International Journal of Molecular Sciences, 25 (5). ISSN 1422-0067

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Official URL: https://www.mdpi.com/1422-0067/25/5/3005

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, V2O5 and Nb2O5, on the thermal, (micro)structural, and electrical properties of the 35Na(2)O-25V(2)O(5)-(40 - x)P2O5 - xNb(2)O(5) system is examined. The starting glass shows the highest values of DC conductivity, sigma(DC), reaching 1.45 x 10(-8) Omega(-1) cm(-1) at 303 K, along with a glass transition temperature, T-g, of 371 degrees C. The incorporation of Nb2O5 influences both sigma(DC) and T-g, 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 sigma(DC) arises from a diminishing contribution of polaronic conductivity due to the decrease in the relative number of V4+ ions and the introduction of Nb2O5, 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 V2O5 content on the electrical transport mechanism, a comparative analysis of two analogue series with varying V2O5 content (10 and 25 mol%) is conducted to evaluate the extent of its polaronic contribution.

Item Type:

Article

Uncontrolled Keywords:

phosphate glasses; phosphate glass–ceramics; (micro)structure–property relationship; PXRD; SEM-EDS; EPR; vibrational spectroscopy; impedance spectroscopy; electrical properties

Subjects:

NATURAL SCIENCES > Chemistry
NATURAL SCIENCES > Biology > Biochemistry and Molecular Biology

Divisions:

Division of Materials Chemistry

Projects: