PREPARATION AND CHEMICAL-PROPERTIES OF MAGNESIUM ALUMINUM-OXIDE SOLID-SOLUTIONS

Magnesium aluminium oxide solid solutions were prepared by thermal decomposition of hydrotalcite-like compounds, left bracket Mg//1// minus //xAl//x(OH)//2 right bracket (CO//3)//x/////2 multiplied by (times) mH//2O, at 500-700 degree C. The NaCl-type solid solutions with a cation defect structure of Mg//2//(//1// minus //x//)/////(//2// plus //x//) Al//2//x/////(//2// plus //x//) D'ALEMB //x/////(//2// plus //x//) O were formed in the range 0. 15 less than equivalent to Al/(Mg plus Al) less than equivalent to 0. 33. Magnesium aluminium oxide hydrated and took up carbonate ion from aqueous solution to reconstruct the hydrotalcite-type structure. Phosphate was also taken up, at a rate that decreased with increasing thermal decomposition temperature from 500 to 700 degree C, although the nature of the product in this instance was not established. The solid solutions decomposed above 1000 degree C to MgO and MgAl//2O//4, which showed no capacity to take up anions.