Single-calcination synthesis of pyrochlore-free 0.9Pb(Mg1/3Nb2/3)O3-0.1PbTiO3 and Pb(Mg1/3Nb2/3)O3 ceramics using a coating method

A coating approach for synthesizing 0.9Pb(Mg1/3Nb2/3)O-3-0.1PbTiO(3) (0.9PMN-0.1PT) and PMN using a single calcination step was demonstrated. The pyrochlore phase was prevented by coating Mg(OH)(2) on Nb2O5 particles. Coating of Mg(OH)(2) on Nb2O5 was done by precipitating Mg(OH), in an aqueous Nb2O5 suspension at pH 10. The coating was confirmed using optical micrographs and zeta-potential measurements. A single calcination treatment of the Mg(OH)(2)-coated Nb2O5 particles mixed with appropriate amounts of PbO and PbTiO3 powders at 900degreesC for 2 h produced pyrochlore-free perovskite 0.9PMN-0.1PT and PMN powders. The elimination of the pyrochlore phase was attributed to the separation of PbO and Nb2O5 by the Mg(OH)(2) coating. The Mg(OH)(2) coating on the Nb2O5 improved the mixing of Mg(OH)(2) and Nb2O5 and decreased the temperature for complete columbite conversion to similar to850degreesC. The pyrochlore-free perovskite 0.9PMN-0.1PT powders were sintered to 97% density at 1150degreesC. The sintered 0.9PMN-0.1PT ceramics exhibited a dielectric constant maximum of similar to24 660 at 45degreesC at a frequency of 1 kHz.