Kinetic Study of Vapor-Phase Preparation of Orthorhombic Molybdenum Trioxide

Abstract

A new kinetic approach to study the vapor-phase preparation of orthorhombic molybdenum trioxide (MoO 3 ) has been established in this work. Using a simple experimental setup, the vaporization and condensation of MoO 3 can be investigated with sufficient oxygen background to ensure the stoichiometry of the compound. The empirical condensation rate of the MoO 3 obtained in the temperature range 642-660°C is R E ) 1.20 × 10 -3 ∆P 2.07 , where ∆P is the partial pressure difference of MoO 3 between the source and condensed crystals. On the basis of the observed crystal morphology and XRD results, a more precise MoO 3 condensation kinetic model has been developed to explain the layer-by-layer growth of orthorhombic structure. The staged growth phenomena can be interpreted by this mechanistic model, which correlates the condensed MoO 3 weight data to the experimental setup. The driving force of the condensation growth is investigated with respect to the current experimental conditions. For the MoO 3 partial pressure ratios of 3.86-2.97 between the source and condensed MoO 3 , free energy changes determined for the growth are in the range -10.7 to -8.8 kJ/mol.

Morphology evolution and quantitative analysis of β-MoO3 and α-MoO3

“…When roasting β-MoO 3 in air, the samples have enough opportunity to interact with O 2 . Maximum interaction between air and β-MoO 3 is important to ensure that the following chemical equilibrium is shifted to the left [28]:…”

Sublimation growth and vibrational microspectrometry of α-MoO3 single crystals

“…Later method seems to be optimal to have high-quality crystals. Comparatively high vapor pressure at sublimation temperatures of T¼ 600-700 1C provided a possibility to grow the a-MoO 3 platelet crystals of 450-200 mm size range [21,22,30]. The crystals were characterized by layer-bylayer growth mechanism and presence of echelons of (0 1 0) terraces that is an indicator of structural quality.…”

Complex α-MoO3 Nanostructures with External Bonding Capacity for Self-Assembly

“…Many functional materials are structurally anisotropic, which may lead to variation in growth rates along different crystallographic directions in the synthesis. , If we can switch on and off the crystal growth along a specific crystallographic direction at a particular time, in principle, crystals with complex geometric forms can be engineered . Recently, we have developed a hydrothermal method to grow one-dimensional (1D) α-MoO 3 and 2H-MoS 2 nanorods with a subsequent sulfidation …”