Reaction Kinetics and Morphological Study of TiNb2O7 Synthesized by Solid-State Reaction

Abstract

Although TiNb 2 O 7 is regarded as a material with high application potential in lithium-ion batteries (LIBs) and solid-oxide fuel cells (SOFCs), it has been difficult to find suitable cost-effective conditions for synthesizing it on a commercial scale. In this study, TiNb 2 O 7 compounds were synthesized by a solid state synthesis process. For stoichiometrically precise synthesis of the TiNb 2 O 7 phase, the starting materials, TiO 2 and Nb 2 O 5 were taken in a 1:1 molar ratio. Activation energy and reaction kinetics of the system were investigated at various synthesis temperatures (800,1000,1200, and 1400°C) and for various holding durations (1,5,10, and 20 h). Furthermore, change in the product morphology and particle size distribution were also evaluated as a function of synthesis temperature and duration. Additionally, quantitative phase analysis was conducted using the Rietveld refinement method. It was found that increases in the synthesis temperature and holding time lead to increase in the mean particle size from 1 to 4.5 μm. The reaction rate constant for the synthesis reaction was also calculated.

Structural Changes During Lithiation of TiNb2O7

“…It is possible to distinguish small primary particles of about 200–500 nm in size, along with larger micrometer-sized agglomerates of smaller primary particles. Note, the conventional ceramic synthesis is usually realized at higher temperatures (up to 1400 °C) and for a longer duration (12–24 h) and results in the formation of inhomogeneous product with large particles (5–20 μm) and wide particle size distribution. ,,, …”

“…Note, the conventional ceramic synthesis is usually realized at higher temperatures (up to 1400 °C) and for a longer duration (12−24 h) and results in the formation of inhomogeneous product with large particles (5−20 μm) and wide particle size distribution. 11,13,16,17 The local structure of the as-prepared TNO was studied by 93 Nb NMR spectroscopy. 93 Nb is a quadrupole nucleus with spin I = 9/2.…”

“…TiNb 2 O 7 can be obtained by various routes, including solution methods (hydrothermal, sol–gel, et al), , which allow one to control the size and morphology of particles, and solid-state ones, which are the most cost-effective. , However, conventional solid-state method requires prolonged heat treatment of a mixture of TiO 2 and Nb 2 O 5 at a high temperature of 1000–1400 °C for 12–24 h and usually results in inhomogeneous product with large particle size ,,, (5–20 μm) and a wide particle size distribution. The combination of the solid-state synthesis with preliminary mechanical activation (MA) makes it possible to reduce the synthesis temperature, the duration of heat treatment and to obtain a homogeneous final product with a submicrometer particle size.…”

Enhanced Energy Storage Performance of Zr-Doped TiNb2O7 Nanospheres Prepared by the Hydrolytic Method

“…In order to relieve the issues suffered by bulk TiNb 2 O 7 , various strategies have been tried, such as introducing an oxygen vacancy, − regulating the morphology, ,− doping with alien ions, − etc. Oxygen vacancy is an intrinsic defect which can trigger lattice distortion and electron concentration improvement .…”

Ultrafast reaction‐sintering of grain size‐controlled titanium niobate from TiO2 and Nb2O5

“…However, these methods are still not feasible to implement in large-scale production, leaving space to explore the more straightforward solid-state synthesis between titania (TiO 2 ) and niobia (Nb 2 O 5 ). 13 These oxides are widely available and react to form TiNb 2 O 7 at high temperatures according to TiO 2 + Nb 2 O 5 → TiNb 2 O 7 . This reaction can be carried by merely mixing reactant powder in a stoichiometric ratio and heating it to sintering temperatures (usually > 1000 • C) to promote a process of reactive sintering.…”