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Journal of Thermal Analysis and Calorimetry
Authors:
D. Gouveia
,
A. Souza
,
M. de Maurera
,
C. da Costa
,
I. Santos
,
S. Prasad
,
J. de Lima
,
C. Paskocimas
, and
E. Longo

Abstract  

Using the Pechini method, pigments with spinel structure (Zn7Sb2O12)were synthesized by substitution of the cation Zn2+ by Co2+, in compounds with different concentrations of Sb2O3. The doping resulted in CoxZn(7–x)Sb2O12 phases(x=1–7) that were isomorphs to spinel, denominated as samples A and B. After thermal treatment at 400C for 1 h, the powders were characterized by thermogravimetry(TG) and differential thermal analysis (DTA). The results indicate a different behavior whena higher amount of Sb2O3 is used, due to the presence of a secondary phase (ilmenite).

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Journal of Thermal Analysis and Calorimetry
Authors:
D. Melo
,
R. M. M. Marinho
,
F. T. G. Vieira
,
S. J. G. Lima
,
E. Longo
,
A. G. Souza
,
A. S. Maia
, and
I. M. G. Santos

Abstract

Perovskite type oxides have been intensively studied due to their interesting optical, electrical, and catalytic properties. Among perovskites the alkaline earth stannates stand out, being strontium stannates (SrSnO3) the most important material in ceramic technology among them due to their wide application as dielectric component. SrSnO3 has also been applied as stable capacitor and humidity sensor. In the present work, SrSnO3:Cu was synthesized by polymeric precursor method and heat treated at 700, 800, and 900 °C for 4 h. After that, the material was characterized by thermal analysis (TG/DTA), X-ray diffraction (XRD), infrared spectroscopy, and UV–vis spectroscopy. Results indicated three thermal decomposition steps and confirmed the presence of strontium carbonate and Cu2+ reduction to Cu+ at higher dopant amounts. XRD patterns indicated that the perovskite crystallization started at 700 °C with strontiatite (SrCO3) and cassiterite (SnO2) as intermediate phases, disappearing at higher temperatures. The amount of secondary phase was reduced with the increase in the Cu concentration.

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Journal of Thermal Analysis and Calorimetry
Authors:
F. T. G. Vieira
,
A. L. M. Oliveira
,
D. S. Melo
,
S. J. G. Lima
,
E. Longo
,
A. S. Maia
,
A. G. Souza
, and
I. M. G. Santos

Abstract

Alkaline earth stannates have recently become important materials in ceramic technology due to its application as humidity sensor. In this work, alkaline earth stannates doped with Fe3+ were synthesized by the polymeric precursor method, with calcination at 300 °C/7 h and between 400 and 1100 °C/4 h. The powder precursors were characterized by TG/DTA after partial elimination of carbon. Characterization after the second calcination step was done by X-ray diffraction, infrared spectroscopy, and UV–vis spectroscopy. Results confirmed the formation of the SrSnO3:Fe with orthorhombic perovskite structure, besides SrCO3 as secondary phase. Crystallization occurred at 600 °C, being much lower than the crystallization temperature of perovskites synthesized by solid state reaction. The analysis of TG curves indicated that the phase crystallization was preceded by two thermal decomposition steps. Carbonate elimination occurred at two different temperatures, around 800 °C and above 1000 °C.

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Journal of Thermal Analysis and Calorimetry
Authors:
J. R. Botelho
,
A. G. Souza
,
A. D. Gondim
,
P. F. Athayde-Filho
,
P. O. Dunstan
,
C. D. Pinheiro
,
E. Longo
, and
L. H. Carvalho
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Journal of Thermal Analysis and Calorimetry
Authors:
M. A. F. Souza
,
R. A. Candeia
,
S. J. G. Lima
,
M. R. Cassia-Santos
,
I. M. G. Santos
,
E. Longo
, and
A. G. Souza
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Journal of Thermal Analysis and Calorimetry
Authors:
Soraia de Souza
,
Mary Alves
,
A. de Oliveira
,
E. Longo
,
F. Ticiano Gomes Vieira
,
Rodinei Gomes
,
L. Soledade
,
A. de Souza
, and
Iêda Garcia dos Santos

Abstract  

In this work, the synthesis of Nd-doped SrSnO3 by the polymeric precursor method, with calcination between 250 and 700 °C is reported. The powder precursors were characterized by TG/DTA and high temperature X-ray diffraction (HTXRD). After heat treatment, the material was characterized by XRD and infrared spectroscopy. Ester and carbonate amounts were strictly related to Nd-doping. According to XRD patterns, the orthorhombic perovskite was obtained at 700 °C for SrSnO3 and SrSn0.99Nd0.01O3. For Sr0.99Nd0.01SnO3, the kinetics displayed an important hole in the crystallization process, as no peak was observed in HTXRD up to 700 °C, while a XRD patterns showed a crystalline material after calcination at 250 °C.

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Journal of Thermal Analysis and Calorimetry
Authors:
Mary Alves
,
Soraia Souza
,
Márcia Silva
,
Elaine Paris
,
S. Lima
,
R. Gomes
,
E. Longo
,
A. de Souza
, and
Iêda Garcia dos Santos

Abstract  

SrSnO3 was synthesized by the polymeric precursor method with elimination of carbon in oxygen atmosphere at 250 °C for 24 h. The powder precursors were characterized by TG/DTA and high temperature X-ray diffraction (HTXRD). After calcination at 500, 600 and 700 °C for 2 h, samples were evaluated by X-ray diffraction (XRD), infrared spectroscopy (IR) and Rietveld refinement of the XRD patterns for samples calcined at 900, 1,000 and 1,100 °C. During thermal treatment of the powder precursor ester combustion was followed by carbonate decomposition and perovskite crystallization. No phase transition was observed as usually presented in literature for SrSnO3 that had only a rearrangement of SnO6 polyhedra.

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Journal of Thermal Analysis and Calorimetry
Authors:
M. A. F. de Souza
,
A. G. Souza
,
R. A. Candeia
,
D. M. A. Melo
,
L. E. B. Soledade
,
M. R. C. Santos
,
I. M. G. Santos
,
S. J. G. Lima
, and
E. Longo
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Journal of Thermal Analysis and Calorimetry
Authors:
S. C. Souza
,
M. A. F. Souza
,
S. J. G. Lima
,
M. R. Cassia-Santos
,
V. J. Fernandes Jr.
,
L. E. B. Soledade
,
E. Longo
,
A. G. Souza
, and
I. M. G. Santos
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