Synthesis of phase pure perovskite compounds

Metal (I) - oxygen - metal (II) bridging bond formation occurs as a consequence of a redox reaction between two metal oxides or hydroxides as mentioned above. It is particularly interesting to apply these principles to the synthesis of complex oxides such as perovskites. Phase pure perovskites, e.g. 

Since Nb205 is a highly acidic oxide while Mg(OH)2 is a highly basic one, a milling of a stoichiometric mixture of these compounds pushes forward the formation 

PMN-PT (x=0 0.2), are actually obtained by heating of milled mixture as a precursor at moderate temperatures as low as 850°C [20,21], Products are finely and homogeneously grained just because of firing at low temperature, Mg(OH 2 (brucite), PbO (massicot), TiOj (anatase and rutile) and NbjOs (orthorhombic) were used as starting materials. Mechanical activation was carried out by using a multi-ring type mill. 

Together with the XRD patterns, this demonstrates that new chemical bonds leading to a perovskite phase are already formed during milling. 

As shown in Fig. 7.7, a pure perovskite phase was obtained after calcining the milled mixture at 850°C for 4 h in air. On the other hand, a cubic pyrochlore (P3N4) phase was predominant with the coexistence of perovsWte and PbO (litharge) on the calcined products from non-milled mixture. When MgO was used instead of Mg(OH)2, no significant change of 

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