Synthesis and Characterization of a [Li<sub>0+x</sub>Mg<sub>2-2x</sub>Al<sub>1+x</sub>(OH)<sub>6</sub>][Cl·mH<sub>2</sub>O] Solid Solution with X = 0 - 1 at Different Temperatures
- 1 Mineralogy/Geochemistry, Institute for Geosciences and Geography, University of Halle, Halle, Germany
- 2 Mineralogy/Geochemistry, Institute for Geosciences and Geography, University of Halle, Halle, Germany
Abstract
The synthesis of a novel Li + /Mg 2+ /Al 3+ containing layered double hydroxide (LDH) by using a hydrothermal synthesis route is represented in this work. The autoclaves were heated up to 100 o C, 120 o C, 140 o C and 160 o C for 10 h and 48 h with a water to solid ratio (W/S) of 15:1. The physicochemical properties of the synthesized LDHs were investigated by X-ray powder diffraction (PXRD), fourier transform infrared spectroscopy (FTIR), thermo gravimetric and differential thermal analysis (TG-DTA), inductively coupled plasma optical emission spectroscopy (ICP-OES) and scanning electron microscopy (SEM). The formation of a solid solution phase depends strongly on the composition of the reactants and the synthesis temperature. Using an exact stoichiometric ratio of Li + /Mg 2+ /Al 3+ resulted in the synthesis of amorphous phases without producing plenty of crystalline amounts of the expected solid solutions while using higher temperatures than 140 o C resulted in a formation of AlO(OH). To avoid the formation of an Al containing amorphous phase or an AlO(OH) crystalline phase, the stoichiometric ratio of Li+ was changed. The results show solid solutions with the formula [Li 0+x Mg 2-2x Al 1+x (OH) 6 ][Cl . mH 2 O] with X ≥ 0.9. The lattice parameters and chemical compositions for solid solutions with different compositions were determined and the pure solid solution with the highest amount of Mg (x = 0.9) is [Li0.9Mg0.2Al1.9(OH)6] [Cl . 0.50H2O] with the lattice parameters a = 5.1004(4) Å , c = 15.3512(1) Å , V = 345.844(9) Å 3. For X < 0.9 two separate phases, a Mg 2+ and a Li + dominated solid solution, are coexistent.
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