半化学法制备0.80Pb(Mg_(1/3)Nb_(2/3))O_3-0.20PbTiO_3陶瓷的反应机理

Reaction Mechanism of 0.80Pb(Mg_(1/3)Nb_(2/3))O_3 -0.20PbTiO_3 Ceramics Prepared by Semichemical Method

采用半化学法制备了纯钙钛矿相的0.80Ph（Mg1/3Nb2/3）O3-0.20PbTiO3（简称为0.80PMN-0.20PT）陶瓷.反应前驱体是以硝酸镁的饱和溶液代替传统氧化物混合法中的氧化镁,与PbO、Nb2O5和 TiO2混合球磨得到的.该前驱体的TG-DTG-DSC和XRD分析表明,半化学法的反应机理不同于传统氧化物混合法和二次合成法的反应机理.在煅烧过程中,硝酸镁与氧化铅反应生成铅的活化中间体Pb6O5（NO3）2,由此活化的PbO或Pb3O4可与Nb2O5生成不稳定的、缺B位的焦绿石相Pb3Nb2O8;再与MgO反应生成钙钛矿相PMN-PT.

The semichemical method was developed for the synthesis of 0.80Pb(Mg1/3Nb2/3)O3-0.20PbTiO3(0.80PMN-0.20PT) ceramics with pure perovskite phase. The precursors were prepared by adding an aqueous Mg(NO3)2 solution rather than MgO to the alcoholic slurry of PbO, TiO2 and Nb2O5. The TG-DTG-DSC and XRD analysis show that the mechanism in this method is different from those of the known columbite or conventional mixed oxide method. Mg(NO3)2 reacts with PbO to form a intermediate of Pb6O5(NO3)2 at milling and calcinations process. The activated PbO and Pb3O4 by the intermediate reacted with Nb2O5 to form an unstable B-deficient pyrochlore structure of Pb3Nb2O8 , which progressively inserts magnesium oxide to transform into PMN-perovskite phase.