CHEMICAL AND STRUCTURAL TRANSFORMATIONS IN MANGANESE ALUMINUM SPINEL OF THE COMPOSITION Mn1.5Al1.5O4 DURING HEATING AND COOLING IN AIR
O. A. Bulavchenko, S. V. Tsybulya, P. G. Tsyrul'nikov, T. N. Afonasenko, S. V. Cherepanova, E. Y. Gerasimov
Keywords: high temperature X-ray diffraction, manganese aluminum systems, phase transformations
Pages: 518-524
Abstract
Single phase cubic spinel of the composition Mn1.5Al1.5O4 is synthesized. Its crystal structure refinement shows that 0.4Mn+0.6Al are in the octahedral sites and 0.7Mn+0.3Al are in the tetrahedral sites. High temperature X-ray diffraction is used to analyze Mn1.5Al1.5O4 behavior during heating and cooling in air. In a temperature range of 600°C to 700°C, initial spinel splits into layers, and the sample represents a two-phase system: cubic spinel Mn0.4Al2.4O4 and a phase based on β-Mn3O4. Above 900°C the sample again turns into single phase cubic spinel. The role of oxidizing processes in the decomposition of Mn1.5Al1.5O4 caused by oxygenation and partial oxidation of Mn2+ to Mn3+ is shown. A scheme of structural transformations of manganese aluminum spinel during heating from room temperature and cooling from 950°C is proposed.
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