Thermodynamic Modeling of R 2 O–V 2 O 5 Systems (R = Li, Na, K, Rb, and Cs) With Key Experimental Study and Its Applications

ABSTRACT

Key phase diagram studies of Li
2
O–V
2
O
5
, K
2
O–V
2
O
5
, and Rb
2
O–V
2
O
5
systems were conducted using X‐ray diffraction and differential thermal analysis within Pt crucibles. The XRD results confirmed the existence of stoichiometric phase Li
4
V
34
O
87
in the Li
2
O–V
2
O
5
system. In the K
2
O–V
2
O
5
system, the melting temperatures of K
2
V
8
O
21
and KVO
3
were experimentally determined to be 532.4°C and 516.5°C, respectively. The eutectic reaction between liquid, Rb
3
V
5
O
14
, and RbVO
3
in the Rb
2
O–V
2
O
5
system was identified at 496°C with a composition of 42 mol% Rb
2
O. The modified quasichemical model (MQM), which accounts for the short‐range ordering of the second‐nearest neighbors of cations in molten oxide solutions, was employed to describe the liquid phase, and compound energy formalism (CEF) was applied to model the Li
1+X
V
3
O
8
solid solution at elevated temperatures. Thermodynamic modeling of the R
2
O–V
2
O
5
(R = Li, Na, K, Rb, and Cs) systems was developed using the CALculation of PHAse Diagrams (CALPHAD) methodology. The experimental data across the entire composition range of the R
2
O–V
2
O
5
systems were successfully reproduced, and thermodynamic properties for all solid and liquid phases within all binary systems were obtained. The developed thermodynamic database was further applied to simulate vanadium extraction processes, with the optimal operation windows.