Chemical co-precipitation of mixed (Pb+Ti) oxalates precursor for the synthesis of PbTiO_3 powders

摘要

A chemical co-precipitation route is developed to precipitate mixed oxalates (PbC_2O_4+ TiOC_2O_4.2H_2O) at room temperature. In this synthesis route, an anionic TiO(C_2O_4)_2~(-2) species obtained by dissolving potassium titanyl oxalate (KTO) (0.01 M) stable over narrow pH range are destabilized with the addition of 0.01 M solution of lead chloride (PbCl_2) to produce insoluble TiOC_2O_4.2H_2O and oxalic acid. The in situ generated oxalic acid during destabilization process reacts with Pb~(2+) ions to precipitate lead oxalate (PbC_2O_4). The mixed oxalates on pyrolysis in air at 750 deg C/4 h produced submicron sized (0.13-0.15 mu m) stoichiometric PbTiO_3 (PT) powders having tetragonal symmetry (with c/a ratio approx 1.063) which form agglomerates of size 0.5 - 5 mu m. Various physico-chemical techniques were used to characterize the as-dried mixed oxalates precursor and PbTiO_3 powders All these experimental results related to synthesis and characterization of these powders are presented in this paper.