Authors:M. Bernardi, E. Antonelli, A. Lourenço, C. Feitosa, L. Maia, and A. Hernandes
The results reported here based on a study
(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.
Authors:S. Santos, M. de Andrade, J. Sampaio, A. da Luz, and T. Ogasawara
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 (Ea) and
reaction order (n) for each stage were
determined using Horowitz–Metzger, Coats–Redfern, Kissinger and
Broido methods. Values of Ea
varying between 257–267 kJ mol–1 and n=0–1 were found. According to the kinetic
analysis the decomposition reactions were diffusion controlled.
Authors:D. Gouveia, R. Rosenhaim, M. de Maurera, S. Lima, C. Paskocimas, E. Longo, A. Souza, and I. Santos
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.
Authors:T. M. Milão, J. F. A. Oliveira, V. D. Araújo, and M. I. B. Bernardi
], solid-state reaction [ 6 ], and Pechinimethod [ 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
the Pechinimethod [ 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
, Pechinimethod (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
Authors:Aleksandra Matraszek, Ewa Radominska, and Irena Szczygiel
the obtained powders, especially the phase purity of the preparations and their morphology and microstructure. The characteristics of the polycrystalline powders produced by the Pechinimethod and through precipitation from solutions containing PO 4 3
Authors:L. da Silva, M. Bernardi, L. Maia, G. Frigo, and V. Mastelaro
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.
Authors:Mary Alves, Soraia Souza, S. Lima, E. Longo, A. Souza, and Iêda Santos
CaSnO3 was synthesized by the polymeric precursor
method, using different precursor salts as (CH3COO)2CaH2O,
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.
Authors:Márcia Silva, L. Soledade, S. Lima, E. Longo, A. Souza, and Iêda Santos
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.