Comments on “tuning electrical conductivity in lithium-doped sodium titanate via sonochemical synthesis”

Abstract

da Silva et al. (Mater. Sci. Eng. B 323 (2026) 118836) recently reported the sonochemical synthesis of lithium-doped sodium titanate Na2-xLixTi3O7 (x = 0, 0.01, 0.02 and 0.03). They proposed three-phase products: (i) lithium-doped Na2-xLixTi3O7 with the layered structure, (ii) undoped Na2Ti6O13 with tunnel structure, and (iii) the NaLiTi3O7 impurity (at high x). It is argued that that the formation of Na2-xLixTi3O7 is unlikely. Two major products could be assigned as undoped Na2Ti3O7 and undoped Na2Ti6O13. Also, the NaLiTi3O7 impurity (which has completely different structure from the layered alkali titanate) could be the structurally related Li4Ti5O12 spinel. The present interpretation can explain the invariant unit cell parameters, the decrease of optical band gap, and the improvement of electrical conductivity observed by the original authors.