AN IR SPECTROSCOPIC INVESTIGATION OF COPPER MANGANITE CUXMN3-XO4 (0-LESS-THAN-X-LESS-THAN-1) SPINELS AND THEIR OXIDATION-PRODUCTS

The IR absorption spectra of tetragonal copper manganite CuxMn3-x(O4) spinels (O < x < 1) have singled out a discontinuity in cation distribution to occur at x > 0.60 in conformity with that recorded by our previous measurements and have warranted the existence of a more complex cation distribution than that proposed earlier. It has been concluded from this study that the ionic configuration for x < 0.60, i.e. (Cux+-Mn1-x2+)A(Mn2-x3+ Mnx4+)BO4(2)-, changes for x > 0.60 to (Cux-y+Mn1-x+y2+)A(Cuy2+Mn2-x-y3+Mnx4+)(B)O4(2-), where y represents a low value (less than 0.20). When the oxidation of Mn2+ and Cu+ ions is achieved below 450-degrees-C, IR absorption measurements confirm the formation of a cation-deficient metastable spinel phase Cu1.5Mn1.5O4+delta with a 1:3 octahedral superstructure.