Interpretation of Li2Al4O7 real structure by means of X-ray- and electron microscopic investigations and the videographic method

Single crystals of the compound Li2Al4O7 have been studied to describe thei r real structure. X-ray-and electron microscopic investigations and the vid eographic method have been employed to characterise the disordered structur e with the unit formula LiAl(2)O(3.5)square(0.5). X-ray photographs reveal symmetry reduction to Pm3m and satellite reflections in < 310 >. The electr on diffraction patterns show real superlattice reflections in < 310 >. Vide ographic real structure simulations yielded that the positions of the satel lite reflections in directions < 310 > are caused by higher frequencies of correlation vectors 1mn < 3m1 >, < 4m2 > and < 5m5 > (1 = a/4, In = b/4, n = c/4) between either oxygen vacancies or Li-ions. Similarly favoured arran gements with correlation vectors < 4m0 > and < 4m4 > can be responsible for the P-lattice reflections. Microhardness data are given.