Thermodynamic measurement of aluminium phosphate by double Knudsen cell mass spectrometry

Abstract

The ion currents of gaseous phosphorus oxides in equilibrium with a mixture of Al 2O 3·P 2O 5 and Al 2O 3 at T = (1473 to 1573) K were measured by double Knudsen cell mass spectrometry. The Gibbs free energy changes of the following reactions estimated in comparison with the ion currents from a mixture of (MgO) 3·P 2O 5 and MgO are as follows: Al 2 O 3 ( s ) + P 2 ( g ) + 5 2 O 2 ( g ) = Al 2 O 3 · P 2 O 5 ( s ) , Δ G ∘ / J = - 1970000 + 574 T / K ( ± 28000 ) for ( 1473 < T / K < 1573 ) .