The synthesis of inorganic materials upon thermal treatment of coordination compoundsis a convenient pathway for getting desired nano-products in pure form and of controlled morphology [1]. Considering the features in the chemistry of lanthanides (Ln) that differentiate themfrom the d-block metals, the design and development of suitable complexes that can be used as precursors is challenging from a synthetic point of view [2]. The problem is getting even more complicated when heterometallic Ln(III)-Bi(III) coordination compounds have to be obtained due to high hydrolysis tendency of Bi(III). Aminopolycarboxylates (APC) proved to be suitable chelating agents for assembling these two metals of a desired ratio within one molecule [3, 4]. Considering all these, the work wasfocussedon the synthesis and investigation of Ln(III)Bi(III)-APC coordination compounds as molecular precursors for the preparation of LnBiO3 mixed oxides (APC = aminopolycarboxylate; Ln(III) = La, Pr, Nd, Gd, Dy, Ho, Er). For this purpose, seven complexes of rare-earth metals with Bismuth(III), having the metals ratio 1:1, were synthesized using triethylenetetraaminehexaacetate (ttha6-) as polydentate ligand. The compositions of the complexes were determined based on the results of the element analysis, IR spectroscopy and thermogravimetry. The results of IR spectroscopy revealed the presence of two series of isostructural complexes, namely LnBi(ttha)·7H2O (Ln(III) = La, Pr, Nd, Gd, Dy) and LnBi(ttha)·10H2O (Ln(III) = Ho, Er). The IR spectra of the compounds from each row are practically identical but different between the two series. Thermogravimetric analysis performed at 10oC·min-1 heating rate, both in nitrogen and oxygen atmospheres, revealed the presence of three consecutive decomposition steps of the precursors: dehydration, organic ligand thermolysis and formation of inorganic residues as a result of decarboxylation.The residual mass, at already 600oC, for the decomposition under oxygen is in good agreement with the formation of the expected LnBiO3 mixed-oxide, while the process is not complete even at 850oC under nitrogen flow. Two different heating rates, 10oC·min-1 and 0.5oC·min-1, have been applied during decomposition aiming at establishing the optimal thermal regime for getting pure LnBiO3 heterometallic oxides. Though, the gravimetric analysis at 10oC·min-1 demonstrated that the masses of the residues are slightly higher than for the expected LnBiO3, powder X-ray diffraction results confirmed the formation of pure mixed-oxides for both heating rates.