Hydrothermal synthesis and structure of a potassium tantalum defect pyrochlore

Potassium tantalate (Kta(sub2)(O,OH)(sub6).1.8H(sub2)O) having a defect pyrochlore structure, was synthesized and its crystal structure determined. An H-type defect pyrochlore was the result of ion exchange. Both K-type and H-type highly crystalline materials absorb argon. High thermal stability and control of acidity is a feature of such materials.