Reaction mechanisms in the formation of perovskite Pb(Fe 1/2 Nb 1/2 )O 3 by molten salt synthesis method

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Abstract
Reaction mechanisms of Pb(Fe1/2Nb1/2)O3 prepared by the molten salt synthesis method using and equimolar mixture of NaCl and KCl have been investigated in the temperature range from 600[ddot]C to 850[ddot]C. Nearly pure perovskite phase, Pb(Fe1/2Nb1/2)O3 with the pyrochlore Pb3Nb4O13(P3 N2) phase less than 3% (as determined by x-ray diffraction) can be prepared at 800[ddot]C for 1 hr. The reaction mechanisms of Pb(Fe1/2Nb1/2)O3 are divided into four steps, namely the formation of 1) Pb3N2O8(P3N) at close to (600[ddot]C, 2) P3N2 and Pb2Fe2O5(P2F) from the reaction of P3N and Fe2O3 at 600 ∼ 700[ddot]C, 3) PFN from the reaction of P3N2 with PbO and Fe2O3 at 650 ∼ 700[ddot]C, and 4) PFN from the reaction of P3N2 with Pb2Fe2O5(P2F) and PbO above 700[ddot]C. These results can be explained as the improved distribution and reactivity of Fe2O3 and the significant formation of the P2F phase in the molten salt.