Effect of high-energy milling on the solid state formation of zinc manganites (ZnxMn3-xO4, 0.5 ≤ x ≤ 1.5) from the system ZnC2O4• 2H2O - n MnCO3 (n = 1, 1.5 and 2)

By combination of TG/DSC and XRPD measurements it has been shown that zinc manganites form (ZnxMn3−xO4 with 0.5 ≤ x ≤ 1.5) starting from mixtures of zinc oxalate dihydrate and manganese carbonate subjected to mechanical activation by high energy milling. Solid solutions ZnOMn3O4-
ZnMn2O4 are the products obtained by the same experimental conditions, when starting
from a physical mixture. Furthermore milling, besides changing the enthalpy of dehydration of zinc
oxalate, induces a partial formation of amorphous Mn3O4 at r. t. In particular ZnMn2O4 can be prepared
by annealing the milled mixture for 18 h at 650 ◦C while a temperature > 1000 ◦C is needed to
prepare ZnMn2O4 from a physical mixture. Finally, the calorimetric data suggest that the mechanism
of the reaction is different in the two kinds of mixtures.