Synthesis and characterization of yttrium-aluminum-iron and yttrium-cerium-iron citric complexes

Fe-, Y-Fe-Al- and Y-Ce-Fe- citrates were synthesized in ethylene glycol （EG） medium under conditions similar to those used in the polymerized complex method. Their elemental composition, IR,^ 13C and ^1H NMR, X-ray photoelectron and Mossbauer spectra were studied, and formulae describing their composition were proposed. The complexes contained EG bonded as adduct and ester with citric acid ligand and did not contain ligands with deprotonated alcoholic groups. The complexes consisted of agglomerated spheres, 0.7-3 μm in diameter. The local composition of the products was established by energy dispersive X-ray microanalysis. The comparison of the number of the ligands, their average electrical charge and the esterification degree of mono-, di- and trimetallic complexes proved the mixed-metal nature of the species studied. The thermal decomposition of the complexes was studied and a general scheme of the processes taking place was proposed. Highly crystalline, phase homogeneous YaFe4AlO12 was produced after heating the respective complex at 1000 ℃. Ce-doped yttrium-iron garnet, similarly prepared, contained traces of CeO2.

Synthesis of the superfine high-entropy zirconate nanopowders by polymerized complex method

The high-purity and superfine high-entropy zirconate nanopowders,namely(Y_(0.25)La_(0.25)Sm_(0.25)Eu_(0.25))_(2)Zr_(2)O_(7)nanopowders,without agglomeration,were successfully synthesized via polymerized complex method at low temperatures for the first time.The results showed that the crystallinity degree,lattice strain,and particle size of the as-synthesized powders were gradually enhanced with the increase of the synthesis temperature from 800 to 1300℃.The as-synthesized powders involved fluorite phase in the range of 800-1200℃while they underwent the phase evolution from fluorite to pyrochlore at 1300℃.It is worth mentioning that the as-synthesized powders at 900℃are of the highest quality among all the as-synthesized powders,which is due to the fact that they not only possess the particle size of 11 nm without agglomeration,but also show high purity and good compositional uniformity.

Influence of variables on the synthesis of CoFe_(2)O_(4)pigment by the complex polymerization method

Synthetic inorganic pigments are most widely used in ceramic applications due to their excellent chemical and thermal stability and their lower toxicity to both human and environment as well.In the present work,black ceramic pigment CoFe_(2)O_(4)has been synthesized by the complex polymerization method(CPM)with good chemical homogeneity.In order to study the influence of variables on the process of obtaining pigment through CPM,2^((5-2))fractional factorial design with resolution III was used.The variables studied in the mathematical modeling were:citric acid/metal concentration,pre-calcination time,calcination temperature,calcination time,and calcination rate.Powder pigments were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),and UV-visible(UV-Vis)spectroscopy.Based on the results,the formation of cobalt ferrite phase(CoFe_(2)O_(4))with spinel structure was verified.The color of pigments obtained showed dark shades,from black to gray.The model adjusted to the conditions proposed in this study due to the determination coefficient of 99.9%and variance(R²)showed that all factors are significant at the confidence level of 95%.

Effect of different starting materials on the synthesis of Ba_(0.8)Ca_(0.2)TiO_(3)

Literature has reported the synthesis of barium calcium titanates by various synthesis methods such as solid state reaction,co-precipitation and polymer precursors.These compounds are usually obtained using calcium carbonate(CaCO_(3)),barium carbonate(BaCO3)and titanium oxide as starting materials.This study investigated the effect of different starting reagents on the synthesis of Ba_(0.8)Ca_(0.2)TiO_(3)(BCT)by complex polymerization method(CPM).Two sets of starting precursors were used:titanium citrate,CaCO_(3)and BaCO3,and titanium citrate and Ba1-xCaxCO3 solid solution precursor.Samples were crystallized at a temperature range from 400℃to 700℃for different time.The obtained powders were characterized by X-ray diffraction(XRD),thermogravimetry(TG)and differential thermal analysis(DTA),and Raman and infrared spectroscopy.The infrared spectroscopy indicated that the chelation processes of Ba,Ca,Ti and CA ions are very similar.The results showed that the use of CaCO_(3)and BaCO3 or Ba1-xCaxCO3 solid solution as precursors does not affect the final properties of BCT powders obtained by CPM.