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Journal of Thermal Analysis and Calorimetry
Authors: M. Bernardi, E. Antonelli, A. Lourenço, C. Feitosa, L. Maia, and A. Hernandes

Abstract  

The results reported here based on a study of BaTi1–xZrxO3 (x=0, 0.2 and 1) nanometric powders prepared by the modified Pechini method. The powder samples annealed from 600 to 1000C/2 h were characterized by thermogravimetric analysis (TG), differential scanning calorimetry (DSC), X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The decomposition reactions of resins were studied using thermal analysis measurements. The barium titanate zirconate system presented just one orthorhombic phase. Furthermore, this study produced BaTiO3 powders with a tetragonal structure using shorter heat treatments and less expensive precursor materials than those required by the traditional methods.

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Abstract  

TiO2–CeO2 oxides for application as ceramic pigments were synthesized by the Pechini method. In the present work the polymeric network of the pigment precursor was studied using thermal analysis. Results obtained using TG and DTA showed the occurrence of three main mass loss stages and profiles associated to the decomposition of the organic matter and crystallization. The kinetics of the degradation was evaluated by means of TG applying different heating rates. The activation energies (E a) and reaction order (n) for each stage were determined using Horowitz–Metzger, Coats–Redfern, Kissinger and Broido methods. Values of E a varying between 257–267 kJ mol–1 and n=0–1 were found. According to the kinetic analysis the decomposition reactions were diffusion controlled.

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Abstract  

With the aim of obtaining materials with applications in pigments, CoxZn7-xSb2O12 spinels were synthesized using the Pechini method. This method consists in the formation of a polymeric net, where the metallic cations are homogeneously distributed. In this work, two types of alcohol (ethyl glycol and ethylene glycol) were used for the synthesis of a zinc antimoniate spinel, CoxZn7-xSb2O12 (x=0-7). The materials were characterized by termogravimetry (TG) and differential thermal analysis (DTA). TG results indicated a decrease in total mass loss when cobalt was added to the solution substituting zinc, for samples prepared using the two different alcohols. Decomposition temperatures, obtained by TG and DTA, presented a decreasing behavior as cobalt was added to the material. In relation to the alcohols, all results indicated a better polymerization of the resin when ethylene glycol was used, being the most indicated one for cation immobilization. X-ray diffraction did not show differences between the two alcohols - both presented the spinel phase (Co, Zn)2.33Sb0.67O4. Samples with higher quantity of cobalt also presented ilmenite phase (Co, Zn)Sb2O6.

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], solid-state reaction [ 6 ], and Pechini method [ 7 ]. Lima et al. [ 8 ] mention the different methods, such as physical and chemical vapor deposition, metal organic vapor-phase epitaxy, microwave plasma deposition, pyrolysis, chemical bath deposition

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the Pechini method [ 20 ], allows for the production of nanocrystalline powder samples at relatively low temperatures. This synthesis produces a polymer network starting from a polyhydroxy alcohol and an alpha-hydroxycarboxylic acid, with metallic

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, Pechini method (also known as the citrate route or polymeric precursor method) has been widely reported for the synthesis of many oxide powders [ 20 – 24 ]. Invented by Pechini [ 25 ], this process involves a polyester-type resin formation which

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the obtained powders, especially the phase purity of the preparations and their morphology and microstructure. The characteristics of the polycrystalline powders produced by the Pechini method and through precipitation from solutions containing PO 4 3

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Abstract  

This work reports on the synthesis of a SrTi1−xFexO3 nanostructured compound (0.0 ≤ x ≤ 0.1) using a modified polymeric precursor method. The effect of the addition of iron on the thermal, structural and morphological properties of the nanoparticles was investigated by FT-IR spectroscopy, X-ray diffraction, and field emission scanning electron microscopy (FE-SEM). A thermogravimetric analysis indicated that the crystallization process preceded by three decomposition steps. Differential thermal analysis experiments showed that decomposition occurred in a broad range of temperatures from 400 to 600 °C. It was observed that iron ions acted as catalysts, promoting rapid organic decomposition and phase formation at a lower temperature than in SrTiO3. Moreover, the addition of iron decreased the crystallite size and increased the lattice parameter of the SrTi1−xFexO3 structure.

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Abstract  

CaSnO3 was synthesized by the polymeric precursor method, using different precursor salts as (CH3COO)2CaH2O, Ca(NO3)24H2O, CaCl22H2O and CaCO3, leading to different results. Powder precursor was characterized using thermal analysis. Depending on the precursor different thermal behaviors were obtained. Results also indicate the formation of carbonates, confirmed by IR spectra. After calcination and characterization by XRD, the formation of perovskite as single phase was only identified when calcium acetate was used as precursor. For other precursors, tin oxide was observed as secondary phase.

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Abstract  

The present work investigates the influence of milling and calcination atmosphere on the thermal decomposition of SrTiO3 powder precursors. Both pure and neodymium-modified SrTiO3 samples were studied. Milling did not significantly influence numerical mass loss value, but reduced the number of decomposition steps, modifying the profiles of the TG and DTA curves. On the other hand, milling increases the amount of energy liberated by the system upon combustion of organic matter. It was also observed that the milling process, associated to the calcination in an oxygen atmosphere, considerably decreases the amount of organic matter and increases the final mass loss temperature.

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