Thermal stability of organo-chromium or chromium organic complexes and vapor pressure measurements on tris(2,4-pentanedionato)chromium(III) and hexacarbonyl chromium(0) by TG-based transpiration method

Abstract

Thirteen different organo-chromium and chromium organic complexes were synthesized and thermogravimetric studies had been carried out on these complexes in order to search for materials exhibiting high vapor pressure for chemical vapor deposition applications. These studies revealed only two complexes namely tris(2,4-pentanedionato)chromium(III), Cr(acac) 3 and hexacarbonyl chromium(0), Cr(CO) 6 to be vaporizing congruently even at temperatures as low as 500 K , without any decomposition and identifying themselves to be promising candidate materials for coating purposes. A horizontal thermo analyzer was adopted as a transpiration apparatus to measure the vapor pressure of Cr(acac) 3 and Cr(CO) 6 after ascertaining the equilibrium nature of these measurements and by exploiting Dalton's law of partial pressure for ideal gas mixtures. The vapor pressures of Cr(acac) 3 and Cr(CO) 6 were computed to be log(p/ Pa)=14.16(±0.07)−5830(±157) K/T and log(p/ Pa)=11.54(±0.04)−3308(±110) K/T , valid over the ranges 374– 418 K and 309– 347 K and yielding values of 111.6±3.0 and 63.3±2.1 kJ/ mol for their standard enthalpies of sublimation, respectively.