CHEMICAL HYDROGEN INSERTION INTO GAMMA-MANGANESE DIOXIDE EXHIBITING LOW MICROTWINNING

Hydrogen has been inserted by chemical methods into a synthetic gamma- manganese dioxide characterized by 41% de Wolff disorder and a low amo unt of microtwinning. 23 Compounds covering the insertion range 0.00 l ess than or equal to s less than or equal to 0.82 where s is the value in MnO1.966Hs were prepared. Both XRD and FTIR evidence indicated hom ogeneous insertion in the range 0.00 less than or equal to s less than or equal to 0.34 followed by heterogeneous reaction in the range 0.34 less than or equal to s less than or equal to 0.82. Starting from the position that the structure of the predominant ramsdellite type latti ce may be characterized by the distance z between the apical oxygens n ormal to the c axis of the manganese occupied octahedra and the angle beta that the apical vector makes with the b axis a map was developed enabling the structure of the inserted compounds to be followed. In th e homogeneous range, where H+ and e are mobile, insertion led to expan sion of z with little change in beta whereas in the heterogeneous rang e, where H+ is relatively immobile in the final product, a large chang e in beta was observed which is believed to result from the location o f H+ in the final product.