Mn0.15V0.3Mo0.7O3, a New Compound in the MnV2O6–MoO3System

✍ Scribed by Jacek Ziółkowski; Piotr Olszewski; Bogna Napruszewska

• Publisher: Elsevier Science
• Year: 1998
• Tongue: English
• Weight: 229 KB
• Volume: 138
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.1998.7796

✦ Synopsis

In the past we studied the system MnV 2 O 6 (monoclinic, C2/m, brannerite-type structure)-orthorhombic MoO 3 , including the Mn ‫؍‬ Mn 1؊x x V 2؊2x Mo 2x O 6 solid solutions ( ‫؍‬ cation vacancy in the original Mn site, X ‫؍‬ 100x). Mn 's isomorphous with the MnV 2 O 6 matrix appeared to be stable upto X sat ‫؍‬ 42 at room temperature or atmost X sat ‫؍‬ 45 at 520°C. Beyond these limits, Mn sat and o-MoO 3 were observed to coexist. Now, a new phase Mn 0.15 V 0.3 Mo 0.7 O 3 ‫؍‬ Mn 0.3 V 0.6 Mo 1.4 O 6 (or almost, referred to as the Y phase) has been identified in the MnV 2 O 6 -MoO 3 system at formal X ‫؍‬ 70. It is monoclinic P2/m (P2 or Pm) with a ‫؍‬ 11.829(2) A s , b ‫؍‬ 3.657(1) A s , c ‫؍‬ 10.330(2) A s , ‫؍‬ 101.54(1)°, and V ‫؍‬ 437.8(3) A s 3 . The Y phase prepared by a citrate precursor method starts to show reasonable (broadened) XRD reflections at 300°C, becomes predominant at 450°C, and decomposes slowly to Mn sat and o-MoO 3 at higher temperatures (above 450°C). Apparently, due to the parallel course of the solid state reactions, an entirely pure Y phase has never been obtained. Samples with 654X ‫؍‬ 70 always contain some o-MoO 3 traces whereas those with 70 ‫؍‬ X580 are contaminated with Mn sat .

1998 Academic Press

3. RESULTS AND DISCUSSION

First, dealing with C-series samples, we noticed that close to X"70, in addition to the reflections of Mn and