Síntesis en medio poli-alcohólico y caracterización de Perovskitas BaHfO3 y BaZrO3

Abstract

RESUMENLos materiales tipo perovskita (ABO 3 ) presentan considerable interés tecnológico, sus propiedades dependen de los elementos A y B que los sustituyan. Para la elaboración de materiales tipo perovskita se han empleado diversos métodos. En este trabajo se presentan los resultados obtenidos para el BaHfO 3 y BaZrO 3 utilizando la síntesis poliol. Se usaron sales inorgánicas disueltas en dietilenglicol y los materiales recuperados han sido tratados térmicamente a 700 °C y 900 °C. El análisis por difracción de rayos X reveló la estructura cúbica tipo perovskita y se observaron adicionalmente picos correspondientes a las fases secundarias de BaCO 3 y MO 2 (M=Hf o Zr) en ambos materiales. Los espectros obtenidos por FTIR pusieron en evidencia la presencia de BaCO 3 . Las observaciones por microscopía electrónica de barrido revelaron para ambos casos, materiales muy compactos conformados por sub-estructuras más pequeñas en forma de alambre de diámetro aproximado a 900 nm. Para temperaturas de calcinado entre 700 o C y 900 o C se observó un cambio remarcable en la morfología con materiales disgregados conformados por partículas más pequeñas. Los análisis en microscopía electrónica en transmisión revelaron que los materiales tratados a la mayor temperatura están constituidos por pequeños cristales inferiores a 15 nm.Palabras clave: BaHfO 3 , BaZrO 3 , método poliol, perovskita, materiales nanoestructurados. ABSTRACTPerovskite materials (ABO 3 ) present considerable technological interest, their properties depend on the A and B elements. A variety of methods have been used for the elaboration of perovskite materials. In the present paper we present the results of the BaHfO 3 and BaZrO 3 obtained by polyol method. Inorganic salts of barium and hafnium or zirconium were dissolved in di-etilenglicol and the products were heat treated at 700 °C and 900 °C. X-ray diffraction revealed the cubic structure perovskite-type and diffractions corresponding to the secondary phases of BaCO 3 and MO 2 (M=Hf or Zr). The spectra obtained by FTIR show the presence of BaCO 3 . At 700 °C, the scanning electronic microscopy observations revealed a very compact morphology conformed by smaller sub-structures in the form of wire with a diameter around to 900 nm. At 900 °C it was observed a remarkable change in the morphology with dispersed materials conformed by small particles. Transmission electronic microscopy showed that the materials annealed at 900 °C are constituted by small crystals with size lower than 15 nm.

Synthesis of BaHfO3 through with reduction of KOH

“…The appearance of this phase is understandable since the BaHfO3 moisture is susceptible and has already been found in other works [30,[27][28]. To analyze the morphological aspect, the characterization of scanning electron microscopy -SEM- Fig.…”

Lithium and calcium based perovskite type oxides for ethylic transesterification

“…The IR spectrum shows no evidence for the presence of organic intermediates in the samples, except for the band at around 3450 cm −1 , which is related to the O H stretching vibration mode of water molecules [37,38], all peaks are characteristics of the materials studied [37,39]. The bands in the region between 860 and 400 cm −1 indicating the presence of M O bonds [40], while the absorption peaks at approximately 500 cm −1 are assigned to the Zr O vibration [40,41]. However, the CO 2 vibration peaks are observed in the spectrum at 1620-1500 cm −1 , corresponding to C O bond [38,42], most notably for Li 2 ZrO 3 and CaLiZrO 3 oxides.…”