Structure–property relationships in sodium phosphate glasses and glass‐ceramics containing tantalum oxide

Abstract In this study, we examine the impact of structural modifications from incorporating tantalum oxide on the thermal, electrical, and mechanical properties of sodium phosphate glasses and glass‐ceramics. Although these materials are well known for optical applications, this work aims to systematically explore their macroscopic properties, which are yet to be fully characterized. Glass samples were prepared in the binary molar system (100 − x )NaPO 3 – x Ta 2 O 5 with x = {20, 30, 40, 47.5, 50}. A transparent glass‐ceramic was also produced by heat‐treating the 52.5NaPO 3 –47.5Ta 2 O 5 glass composition. Structural characterization was performed by Raman, Fourier transform infrared (FTIR), and solid‐state nuclear magnetic resonance (NMR) spectroscopies. Increasing tantalum oxide content led to a notable increase in glass transition temperature together with a reduced thermal stability against crystallization, indicating higher glass network connectivity at higher tantalum levels. Thermal analysis and X‐ray diffraction (XRD) confirmed the formation of a single crystalline phase in the glass‐ceramic, identified as the bronze‐like perovskite Na 2 Ta 8 O 21 with an average particle size of 31 nm. Electrical properties were investigated using impedance and electric modulus formalisms, revealing that higher tantalum content increases resistivity and decreases conductivity, attributed to reduced Na + ion concentration and increased atomic packing density. Interestingly, glass‐ceramics exhibited slightly higher conductivity than pristine glass. Density, Vickers hardness, Young's modulus, and nanoindentation hardness also increased significantly with higher tantalum content, while crystallization had a minimal effect on these properties. Overall, these results indicate that higher tantalum oxide content not only enhances the glass network's connectivity but also significantly influences the electrical and mechanical properties of sodium phosphate glasses and glass‐ceramics.