Line Profile Analyses of Rhodium Metal Obtained by Decomposition of Rhodium Carbonyl

Abstract

Metal carbonyls are important for chemical vapor deposition (CVD) of metals and alloys and formation of high surface area metallic particles which have potential applications as catalysts. Rhodium carbonyl [Rh{sub 6}(CO){sub 16}] produces high surface area metallic particles whose structure has been reported as monoclinic (I2/a) with lattice dimensions, a=17.00({+-}0.03){Angstrom}, b=9.78({+-}0.02){Angstrom}, c=17.53({+-}0.03){Angstrom} and {Beta}=121{degrees}45` {+-} 30` at room temperature. Generally, metal carbonyl crystals dissociate under vacuum as carbonyl gas and decompose to metallic crystals and carbon monoxide at higher temperatures. However, the behavior of rhodium carbonyl crystals is different; they decompose directly to metallic rhodium without the formation of rhodium carbonyl gas in vacuum. Several residual fine grains of rhodium metal are found after the decomposition in vacuum at relatively low temperatures. The metallic samples of rhodium were obtained from vapor pressure experiments using torsion Knudsen-effusion apparatus. X-ray diffraction analyses performed on these gains showed severely broadened Bragg reflections indicative of small particle size and/or lattice microgram. In this study, a comparison of lattice strains and domain sizes obtained by integral breadth and Fourier methods has been made. In addition a comparison of the lattice strains and domain sizes has been made between the Cauchy, Gaussian, Cauchy-Gaussian and Aqua integralmore » breadth methods.« less