Effect of urea on lead zirconate titanate—Pb(Zr0.52Ti0.48)O3—nanopowders synthesized by the Pechini method

Abreu, Alexandre Santos; Zanetti, S. M.; Oliveira, Maria Auxiliadora; Thim, Gilmar Patrocínio

doi:10.1016/j.jeurceramsoc.2004.02.021

Cited by 49 publications

(20 citation statements)

References 18 publications

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“…Other researchers 20,25 using different amounts of CA and solutions with different pH have shown that the nitrate/CA combustion reaction does not occur below 250 • C when a heating rate of 10 • C min −1 is applied. However, since the present experiments are performed in a furnace pre-heated at 550 • C and reaction (2) occurs readily, we suggest that it takes place before the nitrate/CA combustion.…”

Section: Citric Acid Combustion (Powders Ca05 Ca1 and Ca2)mentioning

confidence: 99%

“…Other authors 20,25 have shown that CA forms a complex with metallic cations and so allows a better homogeneity of the solution. However, complexation was not taken into account here because the duration of the present process (dissolving the nitrates and CA in aqueous solution and the combustion reaction) is much shorter (about 20 min) in comparison with over 3 h in Pechini or sol-gel methods 20,25 and no precipitate was observed and because neither pH adjustment nor evaporation process were performed in the present work.…”

Section: Citric Acid Combustion (Powders Ca05 Ca1 and Ca2)mentioning

confidence: 99%

“…However, complexation was not taken into account here because the duration of the present process (dissolving the nitrates and CA in aqueous solution and the combustion reaction) is much shorter (about 20 min) in comparison with over 3 h in Pechini or sol-gel methods 20,25 and no precipitate was observed and because neither pH adjustment nor evaporation process were performed in the present work. Furthermore, this would not fundamentally change the redox reaction.…”

Section: Citric Acid Combustion (Powders Ca05 Ca1 and Ca2)mentioning

confidence: 99%

“…However, the apparent volume for powders CAU2a and CAU2b is significantly higher than for powder CAU2c (Table 1). Abreu et al 25 showed that excess urea causes modifications of the gel formation in a modified Pechini method. It is thus proposed that the viscosity of the concentrated solution prior to the combustion should also be taken into account.…”

Section: Combustion Using a Mixture Of Citric Acid And Urea (Cau Powdmentioning

confidence: 99%

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Synthesis of the metastable α-Al1.8Fe0.2O3 solid solution from precursors prepared by combustion

Cordier

Peigney

Grave

et al. 2006

Journal of the European Ceramic Society

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OATAO is an open access repository that collects the work of Toulouse researchers and makes it freely available over the web where possible. AbstractThe aim of the paper is to synthesise ␣-Al 1.8 Fe 0.2 O 3 solid solutions from precursors prepared by the nitrate/fuel combustion synthesis route, using either citric acid or urea, or a mixture of both as the fuel, and different fuel/nitrates ratios. In a first part, global reactions are proposed for each synthesis, which are useful to explain the differences in powder volume, morphology, crystallisation state and specific surface area reported in the second part of the study. In a third part, the powders were further calcined at 1100 • C in order to obtain the corundum form. A combination of Mössbauer spectroscopy, XRD and specific surface area measurements revealed that only the powders prepared with Φ e = 2 are the desired monophased ␣-Al 1.8 Fe 0.2 O 3 solid solutions.

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Section: Citric Acid Combustion (Powders Ca05 Ca1 and Ca2)mentioning

confidence: 99%

Section: Citric Acid Combustion (Powders Ca05 Ca1 and Ca2)mentioning

confidence: 99%

Section: Citric Acid Combustion (Powders Ca05 Ca1 and Ca2)mentioning

confidence: 99%

Section: Combustion Using a Mixture Of Citric Acid And Urea (Cau Powdmentioning

confidence: 99%

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Synthesis of the metastable α-Al1.8Fe0.2O3 solid solution from precursors prepared by combustion

Cordier

Peigney

Grave

et al. 2006

Journal of the European Ceramic Society

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“…La primera modificación permite garantizar la homogeneidad de cada uno de los precursores en la solución final; investigaciones [12,13], han demostrado que esta modificación mejora las características microestructurales de los polvos cerámicos. La segunda modificación se fundamenta en la experiencia de trabajos de investigación desarrollados en el grupo CYTEMAC y otros investigadores [14,15,16], que han demostrado que esta adición favorece que polvos cerámicos obtenidos presenten buenas características microestructurales.…”

Section: Materiales Y Métodosunclassified

Obtención de polvos cerámicos de BNKT-KNN por el método Pechini

Bó¹,

Boschi²,

Hotza³

2013

Bol. Soc. Esp. Ceram. Vidr.

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INTRODUCCIÓNEntre las cerámicas piezoeléctricas libres de plomo, el (Bi 1/2 Na 1/2 )TiO 3 (BNT) es considerado un candidato prometedor debido a su gran polarización remanente (38μC/cm 2 ) y su alta temperatura de Curie (320 ºC) y a la presencia de contornos de fase morfotrópicos (CFM) en algunos sistemas basados en BNT, que generalmente exhiben mejores propiedades piezoeléctricas que el BNT. La estructura del BNT es tipo perovskita ABO 3 distorsionada, con grupo espacial R3c a temperatura ambiente. Muchas investigaciones estructurales se han realizado en el BNT desde que fue descubierto en 1960 por Smolenskii y colaboradores [1]. A medida que aumenta la temperatura, el compuesto experimenta una transformación de fase de romboédrica a tetragonal y, finalmente a fase cúbica, con temperaturas de transición de fase de 300 ºC (romboédrica-tetragonal) y 540 ºC (tetragonal-cúbica), lo que fue inicialmente reportado por Zvigzds et al. [2]. Recientemente Jones y Thomas han indicado que la coexistencia de las fases romboédrica-tetragonal y tetragonal-cúbica se produce durante el calentamiento entre 255-400 ºC y 500-540 ºC, respectivamente [3].A pesar de las cualidades ya mencionadas presentadas por el BNT, existen aún problemas que dificultan su implementación en dispositivos electrónicos, tales como sus altos valores de campo coercitivo y conductividad a alta temperatura [4] lo que dificulta el proceso de polarización del material. Lo anterior ha llevado que un gran número de investigaciones se hayan enfocado en mejorar las propiedades eléctricas de este sistema mediante la formación de soluciones sólidas con otros sistemas que posean estructura tipo perovskita, llevando a mejorar las propiedades dieléctricas y, consecuentemente, facilitando su proceso de polarización. Entre los compuestos elegidos se destacan el Bi 0.5 K 0.5 TiO 3 (BKT)[5] y el K 0.5 Na 0.5 NbO 3 (KNN) [6], siendo que la solución sólida 0,97[(Bi 1/2 Na 1/2 ) 1-x (Bi 1/2 K 1/2 ) x TiO 3 ]-0,03[(Na 1/2 K 1/2 )NbO 3 ] (BNKT-KNN) ha presentado valores altos de factor de acoplamiento electromecánico y de permitividad eléctrica [7].Ahora bien, las propiedades de un producto cerámico cualquiera en su estado final, es decir luego del conformado y del proceso de sinterización, dependen en gran medida de la naturaleza y características de los polvos utilizados como material de partida. En la síntesis de materiales, parámetros tales como tamaño y morfología de partícula, entre otros, pueden determinar la aplicación tecnológica del El método Pechini fue utilizado para obtener polvos cerámicos finos y monofásicos del sistema ferroeléctrico libre de plomo 0,97[(Bi 1/2 Na 1/2 ) 1-x (Bi 1/2 K 1/2 ) x TiO 3 ]-0,03[(Na 1/2 K 1/2 )NbO 3 ] ó BNKT-KNN (x = 0.00, 0.18, 0.21, 0.24, 0.27). Este método permitió la obtención de polvos con 100 % de fase perovskita, para el sistema de interés en todas las estequiometrias estudiadas, a una temperatura tan baja como 600 ºC, lo que fue confirmado por difracción de rayos X. Por medio de espectroscopia infrarroja, FT-IR, se pudo determ...

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Synthesis of Nb Doped Lead Zirconate Titanate by Chemical Methods

et al. 2006

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analyser. Oxidation of the Al powder was carried out under compressed air, with a flow rate of 100 ml min -1 , at isothermal temperatures of 400, 450, 500 and 550°C for up to 60 min. Gas release from as-received and TiH 2 powders heat treated at isothermal temperatures of 400, 450, 500 and 550°C for 60 min, was characterised by heating under argon at a rate of 10 Jmin -1 . In all cases, approximately 20 mg of powder was used and the results were normalised for equal mass. Oxygen analysis of as-received and heat treated Al powders and compacts was performed using a LECO analysing system which enables the oxygen content (in wt.%) to be measured to 3 decimal places.Foaming behaviour: Al-TiH 2 precursors were foamed in a mechanical expandometer in which foam expansion was monitored in-situ versus time. The expandometer is constructed from a moving piston, which rests on top of a precursor, which expands in a tubular mould, and is connected to a counterweight by a thin wire. [5] The 22 mm diameter stainless steel mould, foamable precursor and piston were placed in a vertical tube furnace which was pre-heated to 800°C. The measured precursor temperature reached a maximum of 780°C after foaming for roughly 450 s. Foam expansion was measured and recorded to a computer via a linear variable displacement transducer attached to the counterweight. Some precursors were also foamed in a cylindrical stainless steel mould placed in a furnace pre-heated at 800°C. Foaming times of 330, 360 and 480 s were adopted in order to capture the macrostructures during the initial, maximum and collapse phases of the expansion process.Foam samples were sectioned longitudinally, along the mid-plane, using electro-discharge machining to minimise damage to the cell wall structure. Contrast in the foam structure was enhanced by spraying matt black paint over the surface of the samples and then removing it from the sectioned cell walls by light grinding on SiC papers. The painted foams were scanned using a HP Scanjet 6100C at resolution of 100 dpi. For microstructural investigation, the samples were mounted in cold-setting epoxy resin with an electrical contact at the back, ground and polished, finishing with a 1 lm diamond wheel. To reveal grain contrast, the samples were anodised in a solution of 2 % HBF 4 in water, for 45 sec. at 30 V, and viewed in an optical microscope under cross-polarised light.Wet chemical routes for the synthesis of lead zirconate titanate electroceramics have been extensively investigated in order to achieve more reactive powders with a low stoichiometric fluctuation and nanometer dimension of primary particles. Among these, coprecipitation of hydroxides, oxalates, peroxo-hydroxides, and mixture of hydroxides and oxalates has practical advantages (low cost starting materials, good chemical yields) but is limited by preferential precipitate formation and incomplete precipitation. [1][2][3][4] The main consequence of the low control of the precipitation kinetics is the formation of intermediate phases (PbTiO 3 ) during th...

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Effect of urea on lead zirconate titanate—Pb(Zr0.52Ti0.48)O3—nanopowders synthesized by the Pechini method

Cited by 49 publications

References 18 publications

Synthesis of the metastable α-Al1.8Fe0.2O3 solid solution from precursors prepared by combustion

Synthesis of the metastable α-Al1.8Fe0.2O3 solid solution from precursors prepared by combustion

Obtención de polvos cerámicos de BNKT-KNN por el método Pechini

Synthesis of Nb Doped Lead Zirconate Titanate by Chemical Methods

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