Lead magnesium niobate, Pb(Mg,,3Nb213)03 (PMN), was pre-11. Experimental Procedure pared by a sol-gel technique using alkoxide precursors. The hydrolysis-condensation mechanism leads to a translucent gel which is dried under hypercritical conditions to avoid collapse of the porous texture. After drying, the aerogel exhibits a B-deficient pyrochlore structure which progressively inserts magnesium oxide when the temperature increases. Near PMN-perovskite phase. Above 1000°C, the loss of lead oxide mation of an A-deficient pyrochlore phase. [