ZnO‐activated formation of phase pure perovskite Pb(In_1/2Nb_1/2)O₃‐Pb(Zn_1/3Nb_2/3)O₃‐PbTiO₃ powder

Abstract

This paper reports on the phase formation of perovskite Pb(In 1/2 Nb 1/2 )O 3 -Pb(Zn 1/ 3 Nb 2/3 )O 3 -PbTiO 3 (PIN-PZN-PT) powder when doped with 0.04 to 0.83 mol% ZnO. Air calcination of undoped powder mixtures for 4 hours at 800°C resulted in a mixture of Pb 2 Zn 0.29 Nb 1.71 O 6.565 pyrochlore, PIN-PZN-PT perovskite, and In 2 O 3 . ZnO dopant concentrations as low as 0.04 mol% increased the rate of perovskite formation and resulted in near phase pure perovskite powder of 0.5 μm particle size when heated at 800°C in air. In all cases PbTiO 3 and Pb(In 1/2 Nb 1/2 ) O 3 formed prior to PIN-PZN-PT formation. ZnO doping promotes perovskite phase formation by increasing the reactivity of the intermediate pyrochlore phase by substituting Zn 2+ on Nb 5+ sites and forming oxygen vacancies when heated in air. Heating in high P O 2 resulted in an incomplete reaction and a mixture of perovskite and pyrochlore whereas low P O 2 resulted in phase separation into a mixture of rhombohedral perovskite, tetragonal perovskite, and pyrochlore. The P O 2 sensitivity clearly shows that oxygen vacancies due to ZnO-doping are critical for synthesis of phase pure PIN-PZN-PT powder.