Hey everyone.
I want to produce CrO4 gas in order to use that to get a thin film of CrO2 in an ultrahigh vacuum system.
Does anyone know a solid source which can produce CrO4 by heating?
Any help will be very much appreciated.solo - 19-9-2006 at 05:00
CHROMIUM AND CHROMIUM COMPOUNDS IARC MONOGRAPHS VOLUME 49
Excerp
Anhydrous chromic oxide is produced commercially by heating chromic hydroxide, by heating dry ammonium dichromate, or by heating sodium dichromate
with sulfur and washing out the sodium sulfate (Sax & Lewis, 1987). The hydrated material is made commercially by calcining sodium dichromate with
boric acid and hydrolysing chromic borate (IARC, 1980a)
Attachment: chromates.pdf (986kB) This file has been downloaded 4569 times
12AX7 - 19-9-2006 at 07:52
CrO4 only exists as an ion, or possibly a complex. CrO4(0) gas does not exist at any temperature, as far as I know.
If you want to deposit CrO2...duhr why don't you just sputter CrO2...!?
Timwoelen - 19-9-2006 at 10:17
There exists a gaseous chromium compound. It is CrO2Cl2. It is a very volatile liquid, which gives off orange/red vapors. I made some of this. I'm not
sure whether it easily makes CrO2. On long standing, it slowly decomposes, giving off chlorine gas.
Beware of chromyl chloride - Cr(VI) is a serious carcinogen, and chromyl chloride is very volatile...
(It is cool stuff though )JohnWW - 22-9-2006 at 04:12
The highest oxide of Cr is CrO3, which forms orange platey crystals, and readily dissolves in water to give a solution of H2CrO4, a strong acid. When
I was doing my Chemistry degree, I used the solution to remove traces of organic matter from glassware.
If CrO4 exists, it would be a peroxide. I have read somewhere of dark blue peroxychromates having been rprepared.woelen - 22-9-2006 at 08:25
CrO4 does not exist. A compound CrO5 does exist though. This, however, is a mixed oxide/peroxide, and best can be written as CrO(O2)2. It can be made
by adding 10% icecold H2O2 to icecold acidified solution of K2Cr2O7 and then shaking with ether. The ether extracts the CrO5. CrO5 is a beautiful deep
blue/indigo compound. Unfortunately, CrO5 is quite unstable and decomposes quickly at room temperature.
Title: Epitaxial growth of CrO2 thin films by chemical-vapor deposition from a Cr8O21 precursor
Author(s): Ivanov PG, Watts SM, Lind DM
Source: JOURNAL OF APPLIED PHYSICS 89 (2): 1035-1040 JAN 15 2001
Document Type: Article
Language: English
Cited References: 34 Times Cited: 17 Find Related Records Information
Abstract: Presently, the best epitaxial thin films of CrO2 are made by chemical-vapor deposition (CVD) in a two-zone furnace with oxygen flow from a
CrO3 precursor. The growth mode has previously been described as CrO3 vaporizing in the first zone, and thermally decomposing at higher temperature in
the second zone onto a substrate. In the more recent works, the focus has been on the properties of the obtained layers rather than on deposition
mechanisms. In the present experimental work, we attack the epitaxial growth of CrO2 by two completely different methods, namely, molecular-beam
epitaxy (MBE) and CVD. We focus on the CVD process itself, and show the importance of an intermediate compound, Cr8O21, for the growth of CrO2 films.
We show that it is not necessary to start the CVD from CrO3; instead, one can prepare Cr8O21 ex situ, and use it directly for the growth of
high-quality CrO2 epitaxial layers, avoiding any contamination caused by the decomposition of CrO3 to Cr8O21. We discuss in parallel our failed
attempts to deposit CrO2 from either CrO3 or Cr and oxygen plasma by MBE and our experiments with the CVD process, and conclude that CrO3 does not
decompose directly to CrO2 and oxygen, as was expected. We propose a hypothesis that the role of Cr8O21 in the CVD process is to exude unstable
molecules of CrO4, and that the reaction on the substrate is the decomposition CrO4--> CrO2+O-2. (C) 2001 American Institute of Physics.
KeyWords Plus: MAGNETIC-PROPERTIES; LARGE MAGNETORESISTANCE; CHROMIUM; SUPERLATTICES
Addresses: Ivanov PG (reprint author), Florida State Univ, Dept Phys, Tallahassee, FL 32306 USA
Florida State Univ, Dept Phys, Tallahassee, FL 32306 USA
Florida State Univ, Ctr Mat Res & Technol, Tallahassee, FL 32306 USA
Publisher: AMER INST PHYSICS, 2 HUNTINGTON QUADRANGLE, STE 1NO1, MELVILLE, NY 11747-4501 USA
Subject Category: Physics, Applied
IDS Number: 387WG
ISSN: 0021-8979chemrox - 16-10-2007 at 22:06
Quote:
I used the solution to remove traces of organic matter from glassware.
Didn't you mix this with con H2SO4?
[Edited on 16-10-2007 by chemrox]Sauron - 17-10-2007 at 06:25
With all due respect to that JAP article, I think the existance of CrO4 is nothing but a hypothesis as an unstable intermediate in a CVD process. Was
any instrumental evidence for the existance of CrO4 put forward?
This is voodoo chemistry, of the sort one might expect from people in a different discipline.
Sauron, you are right
pprius2006 - 18-10-2007 at 08:59
"...I think the existance of CrO4 is nothing but a hypothesis as an unstable intermediate in a CVD process. Was any instrumental evidence for the
existance of CrO4 put forward?"
Sauron, you are right.
As an expert this is your chance to become the first who hes provided an instrumental evidence. Make some Cr8O21 and figure out what gas comes out
of it at 260C.woelen - 18-10-2007 at 12:51
Is Cr8O21 a well-established oxide of chromium? I could not find anything about it in my books. If it exists, what is the structure of this compound?
Sounds interesting.UnintentionalChaos - 18-10-2007 at 14:36
"Cr8O21 is mentioned here http://adsabs.harvard.edu/abs/1991JSSCh..94..281N"
UnintentionalChaos, that is the best article I know about Cr8O21. It is not only mentioned - the whole article is about Cr8O21.UnintentionalChaos - 22-10-2007 at 12:22
So I mixed up some terminology...you understood what I meant, though.
)