Molecular Precursors for Ferroelectric Materials: Synthesis and Characterization of Bi2M2(mu-O)(sal)4(Hsal)4(OEt)2 and BiM4(mu-O)4(sal)4(Hsal)3(oIPr)4 (sal - O2CC6H4O, Hsal - O2CC6H4OH) (M - Nb, Ta)

Reactions between triphenyl bismuth, salicylic acid, and niobium or tantalum ethoxide have been explored. Four new coordination complexes incorporating bismuth and the group 5 metals niobium or tantalum have been synthesized and characterized spectroscopically, by elemental analysis, and by single crystal X-ray diffraction. The new complexes are Bi2M2(mu-O)(sal)4(Hsal)4(OEt)2 (1a, M- Nb; 1b, M -Ta) and BiM4(mu-O)4(sal)4(Hsal)3(OiPr)4 (sal = O2CC6H42-0, Hsal = O2CC6H4-2-OH) (2a, M = Nb; 2b, M = Ta). Complexes 1a and 1b are isomorphous, as are 2a and 2b. The thermal and hydrolytic decomposition of 1a has been explored by DT/TGA and powder X-ray diffraction, while scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) were used to characterize the morphology and composition of the oxides. The heterobimetallic molecules are completely converted to the amorphous bimetallic oxide by heating to 500 °C in air. Decomposition of 1a or 1b at 650 °C produces the metastable high temperature form of BiNbO4 as the major crystalline oxide phase. Heating samples of 1a to 850 °C favors conversion of the materials to the low temperature phase as well as disproportionation into Bi5Nb3Ois and Nb2O5. Thermal decomposition of 1a and 1b produces porous oxides, while hydrolytic decompostion of the complexes has been shown to produce nanometer scale bimetallic oxide particles. The potential of the complexes to act as single-source precursors for ferroelectric materials is considered.