Influence of doping on the preferential growth of α-MoO 3

L.G Pereira,L.E.B Soledade,J.M Ferreira,S.J.G Lima,V.J Fernandes,A.S Araújo,C.A Paskocimas,E Longo,M.R.C Santos,A.G Souza,I.M.G Santos

doi:10.1016/j.jallcom.2007.04.267

Abstract

MoO 3 is a lamellar material with applications in different areas, as solid lubricants, catalysis, solar cells, etc. In the present work, MoO 3 powders, synthesized by the polymeric precursor method, were doped with nickel or cobalt. The powder precursors were characterized by TG/DTA. After calcination between 500 and 700 °C, the samples were characterized by X-ray diffraction, infrared and Raman spectroscopy and scanning electron microscopy. β-MoO 3 was obtained after calcination at low temperatures. With the temperature increase, α-MoO 3 is observed, with a preferential growth of the (0 2 k 0) planes, when the material is doped and calcined at 700 °C. Doping with nickel increases five times the preferential growth. As a consequence, plate-like particles are observed.

Highlights

With distinctive properties of electrochromism, thermochromism and photochromism as a smart material, gas sensor, catalyst and a host material for intercalation, MoO3 has been extensively investigated over the past decades [1,2,3,4,5,6,7]
The first step is attributed to the loss of water and adsorbed gases, whereas the other steps are ascribed to the combustion of the organic matter
The polymeric precursor method was shown to be efficient for the synthesis of pure and Co- and Ni-doped MoO3 powders at low temperatures, 500–700 ◦C

Summary

Introduction

With distinctive properties of electrochromism, thermochromism and photochromism as a smart material, gas sensor, catalyst and a host material for intercalation, MoO3 has been extensively investigated over the past decades [1,2,3,4,5,6,7]. As a wide bandgap n-type semiconductor material, molybdenum trioxide has received considerable attention over the last few years because of its many applications in various fields [8]. It is noted that molybdenum trioxide is a good intermediary for the synthesis of other important compounds, such as MoO2, MoS2, MoSe2, Mo, etc [2]. Many works have been published reporting the synthesis of molybdenum trioxide crystals. A new synthesis method of ␤-MoO3 was developed, from a molybdic acid solution obtained via cation exchange of Na2MoO4·2H2O solution with resin. This phase was supported on MCM-41 and its catalytic properties were evaluated [10]. The combined use of X-ray diffraction (XRD) and Raman spectroscopy provides a detailed insight of the short- and long-range ordering of these materials

Experimental

Results and discussion

Conclusions