The mechanism of perovskite 0.1Pb(Mg1/2W1/2)O3-0.6Pb(Ni1/3Nb2/3)O3-0.3PbTiO3 (abbreviated PMW-PNN-PT) phase formation by Semichemical Method has been studied. The precursors were prepared by adding aqueous solution of...The mechanism of perovskite 0.1Pb(Mg1/2W1/2)O3-0.6Pb(Ni1/3Nb2/3)O3-0.3PbTiO3 (abbreviated PMW-PNN-PT) phase formation by Semichemical Method has been studied. The precursors were prepared by adding aqueous solution of Mg(Ac)2 and Ni(AC)2 rather than solid MgO and NiO to the alcoholic slurry of PbO, WO3, Nb2O5 and TiO2. The TG-DTG and DSC of the precursors and XRD analysis of the powders at various calcination temperature showed that the mechanism of this method was different from that of the conventional mixed oxide method. The aqueous Mg(Ac)2 and Ni(Ac)2 reacted with PbO to form basic lead acetate, basic magnesium acetate and basic nickel acetate and so on. With the increase of calcination temperature these basic salt decomposed to form nascent PbO, MgO and NiO, which improved the reactivity and distribution of PbO, MgO and NiO. In addition, the formation of PbWO4 and pyrochlore phase Pb3Nb2O8 in the process was in favor of the pervoskite PMW-PNN-PT phase formation. At the calcining temperature of 850 ℃, the perovskite phase reached 98%.展开更多
The mechanisms of Pb(Fe2/3W1/3)O3(PFW) powders with pure perovskite phase prep ared by semichemical method was proposed. The precursors were prepared by adding an aqueous Fe(NO3)3 solution rather than Fe2O3 to the alc...The mechanisms of Pb(Fe2/3W1/3)O3(PFW) powders with pure perovskite phase prep ared by semichemical method was proposed. The precursors were prepared by adding an aqueous Fe(NO3)3 solution rather than Fe2O3 to the alcoholic slurry of PbO a nd WO3. The TG-DTG-DTA and XRD analysis showed that the mechanism in this meth od was different from those of the known columbite precursor method or conventio nal mixed oxide method. Fe(NO3)3 reacted with PbO to form a intermediate of Pb2( NO3)2(OH)2 and Fe(OH)3 and/or Fe2O3 at milling and calcinations process. The act ivated PbO and Pb3O4 by the intermediate reacted with WO3 to form PbWO4, which r eacted directly with nascent-state Fe2O3 to transform into a pyrochlore structu re of Pb2FeWO6.5 at low calcining temperature. And then the pyrochlore phase pro gressively reacted with Fe2O3 to form perovskite PFW phase. Additionally, the ef fects of excess Fe2O3 on the formation of the perovskite PFW phase have been dis cussed.展开更多
文摘The mechanism of perovskite 0.1Pb(Mg1/2W1/2)O3-0.6Pb(Ni1/3Nb2/3)O3-0.3PbTiO3 (abbreviated PMW-PNN-PT) phase formation by Semichemical Method has been studied. The precursors were prepared by adding aqueous solution of Mg(Ac)2 and Ni(AC)2 rather than solid MgO and NiO to the alcoholic slurry of PbO, WO3, Nb2O5 and TiO2. The TG-DTG and DSC of the precursors and XRD analysis of the powders at various calcination temperature showed that the mechanism of this method was different from that of the conventional mixed oxide method. The aqueous Mg(Ac)2 and Ni(Ac)2 reacted with PbO to form basic lead acetate, basic magnesium acetate and basic nickel acetate and so on. With the increase of calcination temperature these basic salt decomposed to form nascent PbO, MgO and NiO, which improved the reactivity and distribution of PbO, MgO and NiO. In addition, the formation of PbWO4 and pyrochlore phase Pb3Nb2O8 in the process was in favor of the pervoskite PMW-PNN-PT phase formation. At the calcining temperature of 850 ℃, the perovskite phase reached 98%.
文摘The mechanisms of Pb(Fe2/3W1/3)O3(PFW) powders with pure perovskite phase prep ared by semichemical method was proposed. The precursors were prepared by adding an aqueous Fe(NO3)3 solution rather than Fe2O3 to the alcoholic slurry of PbO a nd WO3. The TG-DTG-DTA and XRD analysis showed that the mechanism in this meth od was different from those of the known columbite precursor method or conventio nal mixed oxide method. Fe(NO3)3 reacted with PbO to form a intermediate of Pb2( NO3)2(OH)2 and Fe(OH)3 and/or Fe2O3 at milling and calcinations process. The act ivated PbO and Pb3O4 by the intermediate reacted with WO3 to form PbWO4, which r eacted directly with nascent-state Fe2O3 to transform into a pyrochlore structu re of Pb2FeWO6.5 at low calcining temperature. And then the pyrochlore phase pro gressively reacted with Fe2O3 to form perovskite PFW phase. Additionally, the ef fects of excess Fe2O3 on the formation of the perovskite PFW phase have been dis cussed.
