Thermodynamic Stability of K+-β-Alumina

K₂O activity in K⁺-(α+β)-alumina was determined from emf data of the galvanic cell Pt,O₂,(α+β)-alumina/K⁺-β-alumina/K₂SO₄,SO₂+SO₃+O₂,Pt. K₂O activity in the K⁺-(α+β)-alumina was expressed by the equation log a_k2o (±0.038)=(?18295±120)(K/T)+(0.998±0.110), where 961 K+-β-alumina are discussed: the standard Gibbs energy of formation of K₂O·11Al₂O₃ from K₂O and α-Al₂O₃ and from K, O, and Al; the thermodynamic stabilities of K⁺-β-alumina in the atmospheres of SO_x (x=2, 3) and CO₂; the equilibrium vapor pressure of potassium over K⁺-β-alumina under a constant O₂ pressure; and the stability of K⁺-β-alumina in the molten Na-K alloy.