Synthesis and properties of La_1-x Ca_x Al O₃

Abstract

La 1 -x Ca x Al O 3 (0 ≤ x ≤ 0.6) perovskite-type oxides were prepared by co-precipitation method using metal nitrate salts as cation precursors and NaOH solution as the precipitating agent. Differential thermal analysis (DTA) and thermogravimetric analysis (TGA) results indicate that decomposition of the precursor to the oxide begins at ~ 800°C. Powder X-ray diffraction (XRD) patterns confirm the formation of the perovskite phase. Both undoped and doped lanthanum aluminates show two IR active vibrational modes at 450 and 670 cm −1 which are assigned to AlO 6 octahedra of the oxide matrix. The microstructure and morphology of the compounds show that the particles are nearly spherical in shape and are agglomerated. Electrochemical measurements indicate that the catalytic activity is strongly influenced by lanthanum doping. The highest electrode performance is achieved with large calcium content. Keywords: perovskite oxide, chemical co-precipitation, powder diffraction, electrochemical properties Síntesis y propiedades de La 1-x Ca x Al O 3Se prepararon diferentes óxidos tipo perovskita con formulación La 1 -x Ca x Al O 3 (0 ≤ x ≤ 0.6) mediante método de coprecipitación empleando sales nitrato como precursores catiónicos y NaOH como agente precipitante. Los resultados de análisis térmico diferencial (DTA) y análisis termogravimétrico (TGA) indican que la descomposición del precursor del óxido comienza a ~ 800°C. Los patrones de difracción de rayos-X de polvo (XRD) confirman la formación de la fase perovskita. Los aluminatos de lantano, tanto dopado como no dopado, muestran dos modos vibracionales activos a 450 y 670 cm -1 que se asignan a octahedros AlO 6 de la matriz del óxido. La microestructura y morfología de los compuestos muestran que las partículas son de forma próxima a la esférica y aparecen en forma de aglomerados. Las medidas electroquímicas indican que actividad catalítica se ven fuertemente influenciadas por el dopaje con lantano. La mayor actividad del electrodo se alcanza con altos contenidos de calcio.Palabras clave: óxido perovskítico, coprecipitación química, difracción de polvo, propiedades electroquímicas.

Synthesis and Electrochemical Properties of LaCr1−xCoxO3 (0 ≤ x ≤ 0.5) via Co-precipitation Method

“…The formation of agglomerate is probably due to the nature of the solvent used in the preparation of the precipitate [47]. Similar tendency has been found previously for samarium-doped ceria powders [48], La 1-x Ca x AlO 3 oxides [4], LaAl 1-x Ni x O 3 oxides [30]. It has been shown that treating the precipitate with water and ethanol allows interactions between particles which lead during drying to the formation of chemical bonds.…”

STUDY OF Zn-Ni ALLOY COATINGSMODIFIED BY NANO-AL2O3 PARTICLES INCORPORATION

“…The biaxial stress along the lateral and longitudinal directions with 2D area detector using a standard 2ϴ sin2Ѱ method [19]. The average grain size of the coatings was determined from Xray peak broadening by applying the Scherrer formula [20,21]:…”

The influence of co2⁺ concentration on the electrodeposition of ZnNi films to obtain the ZnNi–co composite coatings

“…Scherrer's formula is used for the determination of the Crystallite sizes of the coatings from the X-ray peak broadening of the (330) diffraction peak [9,10,11,19]:…”