The role of Al+3 on the microstructural and electrical properties of Na1+xAlxTi2-x(PO4)3 NASICON glass-ceramics

• Published in: Journal of alloys and compounds 2020-04, Vol.820, p.1, Article 153148
• Main Authors: Nieto-Muñoz, Adriana M., Ortiz-Mosquera, Jairo F., Rodrigues, Ana C.M.
• Format: Article
• Language: English
• Subjects: Activation energy; Aluminum; Aluminum oxide; Ceramics; Chemical synthesis; Crystallization; Electrical measurement; Electrical modulus; Electrical properties; Electrical resistivity; Glass; Glass ceramics; Grain boundaries; Grain boundary; Grain size; Ion currents; NASICON; Sodium-ion conductor; Solid electrolyte; Solid solutions; Thermal stability; Thermodynamic properties
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2019.153148

Sodium-ion conducting glass-ceramics are synthesized by crystallization of Na1+xAlxTi2-x(PO4)3 (0 ≤ x ≤ 1.4) (NATP) parent glasses. The thermal characterization of glasses is performed by Differential Scanning Calorimetry (DSC) and allowed to determine the glass transition (Tg) and crystallization (Tx) temperatures. An increase in the Tx - Tg parameter is observed, indicating that the thermal stability of glasses against crystallization and also the glass-forming ability increase with the inclusion of Al2O3. The X-ray results show that the NaTi2(PO4)3 phase is the majority phase after the crystallization of the precursor glasses at Tx/ 30 min. X-ray results also confirm that the limit of solid solution is reached for x = 1.0. Electrical measurements indicate that the addition of aluminum ions promotes a decrease in activation energy resulting in the increment of the total ionic conductivity of glass-ceramics by up to five orders of magnitude when compared to the free-aluminum sample. The best sodium-conductive glass-ceramic is obtained for x = 1.0 with a total ionic conductivity of 3.2 × 10−3 S cm−1 at 300 °C and activation energy of 0.47 eV. Using the impedance data converted to the electric modulus formalism, the contribution of the grain and grain boundary in total ionic conductivity is analyzed. Finally, an increase in the average grain size of the glass-ceramics with the addition of aluminum is also observed, which contributes to the enhancement of overall ionic conductivity. •Na1+xAlxTi2-x(PO4)3 NASICON series was synthetized via glass-ceramic route.•The conductivity of NaTi2(PO4)3 is increased by up to five orders of magnitude.•Analysis of grain and grain boundary contributions by electrical modulus.•The addition of Al+3/Na+ improves the grain and grain boundary conductivities.•High concentrations of Al+3 increase the average grain size of glass-ceramics.