Ferroelectric behavior of Pb(Mg1/3Nb2/3)O-3 (PMN) obtained by the sol-gel method

The ferroelectric behavior of lead magnesium niobate perovskite, obtained b y sol-gel methods, has been investigated in three samples with compositions based on Pb(Mg1/3Nb2/3)O-3 (PMN) to which an excess of PbO and MgO has bee n added. Electron probe microanalysis (EPMA) showed a single phase of stoic hiometry PbMg0.33Nb0.68O3.02 in sample 2, PbMg0.36Nb0.69O3.09 in sample 3, and PbMg0.32Nb0.67O3 together with PbO in sample 4. Permittivity measuremen ts reach values higher than 22 000 for sample 2 and 11 000 for samples 3 an d 4. A microstructural. characterization of the first two samples, by means of high-resolution electron microscopy, shows the presence of small domain s of double periodicity inserted in a matrix with a single cubic perovskite structure. The concentration of double domains is higher in the first samp le. The third sample shows a mixture phase due to the presence of PbO. The relationship between microstructure and electrical behavior shows that the permittivity values are related not only to the existence of a single PMN p hase but also to Pb:(Mg + Nb) ratios close to 1 and Mg:Nb ratios close to 0 .5.