The processes involved in the solution combustion synthesis of a-Al 2 O 3 using urea as an organic fuel were investigated. The data describing the influence of the relative urea content on the characteristic features of the combustion process, the crystalline structure and the morphology of the aluminium oxide are presented herein. Our data demonstrate that the combustion of stable aluminium nitrate and urea complexes leads to the formation of a-alumina at temperatures of approximately 600-800 1C. Our results, obtained using differential thermal analysis and IR spectroscopy methods, reveal that the low-temperature formation of a-alumina is associated with the thermal decomposition of an a-AlO(OH) intermediate, which was crystallised in the crystal structure of the diaspore.

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The phase composition and structure of equilibrium LaMnO 3 -CaMnO 3 -SrMnO 3 samples prepared at 1500 ° C in air are investigated. The results demonstrate that the system contains a broad region of La 1 − x ( Ca 1 − y Sr y ) x MnO 3 perovskite-like solid solutions in which calcium and strontium cations substitute for lanthanum. The solid solutions have an orthorhombic ( Pnma ), rhombohedral ( ), or tetragonal ( I 4/ mcm ) structure, depending on the A-site cation composition and the nature of lattice distortions. The composition regions of these structures and two-phase regions are mapped out in the LaMnO 3 -CaMnO 3 -SrMnO 3 phase diagram. R3c

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