Zu dem Transportsystem VOTeCl und dem Transportverhalten der Vanadinoxide mit TeCl₄ (I). Der Transport von Vanadindioxid

Abstract

Das thermodynamische Verhalten des Systems V-0-Te-C1 wird beschrieben. Von besonderer Bedeutung fur das Transportverhalten ist der 0,-Koexistenzgleichgewichtsdruck. Fur die Beschreibung des Transportes unterhalb 700 "C ist die Existenz von TeOC1, in der Gasphase Voraussetzung. ALW dem Zusammenwirken des 0,-Koexistenzgleichgewichtsdruckes mit den dominierenden Gasphasenspezies konnen die Transportrichtung, die Transportrate und die Sauerstoffan-und -abreicherung der kristallisierenden Phase berechnet und vorausgesagt werden. V0,-Einkristalle unterschiedlicher Phasenzusammensetzung werden hergestellt.The chemical transport behaviour of the vanadium oxides from V,O, to V,O, with TeCl, is described. The 0, coexistence equilibrium pressure is of especial importance for the transport behaviour. The existence of TeOCl, in the gas phase is the premise for the description of the transport behaviour below 700 O C . The transport direction, the transport rate and the increase or decrease of the oxygen content in the deposited phase, respectively, are calculated from the cooperation of the 0, coexistence equilibrium pressure with the composition in the gas phase. Single crystals of VO, are obtained with different phase compositions.

Chemical Vapor Transport Reactions – A Historical Review

“…. [38,39,40] Further examples for the successful crystallization of mixed-valent oxides with neighboring phases of close-lying composition are the Magnéli phases Ti n O 2n-1 (4 Յ x Յ 10) [41,42] and of the niobium oxides NbO x (2.000 Յ x Յ 2.500). [43,44,45] Crystallization of LaPO 4 was the first example for CVT of an oxide compound containing a complex anion.…”

Chemistry and Physical Properties of the Phosphide Telluride Zr2PTe2

“…This is attributed to the fact that transport effective species exhibit positive and transport agents negative transport efficiencies, respectively, whereas transport efficiencies are zero for species that are not involved in the transport reaction. [16] (5) Admittedly, as a result of the temperature difference between source and sink, secondary gas phase equilibria [Equation (6)] are included in the calculated transport efficiencies as well, which have to be deducted. (6) The effective transport efficiencies received this way are visualised in Figure 8.…”

Chemical Vapor Transport Reactions – Arguments for Choosing a Suitable Transport Agent

“…[20,21,22,23] Thus, all compounds with a composition between V 2 O 3 and VO 2 are transportable under addition of TeCl 4 in a temperature range between 900 and 1000°C. In the case of an initial twophase solid, the phase lower in oxygen will always be the first to be transported in a transport from 1000 to 900°C:…”