• Mader, Werner
• Roy, Subrata Chandra
• Linden, Thomas
• Esser, Lars
• Assenmacher, Wilfried
• Glaum, Robert

Abstract

<jats:title>Abstract</jats:title><jats:p>A series of hitherto unknown mixed-metal phosphates of the monophosphate tungsten bronze structure family [MPTB; (WO<jats:sub>3</jats:sub>)<jats:sub>2<jats:italic>m</jats:italic></jats:sub>(PO<jats:sub>2</jats:sub>)<jats:sub>4</jats:sub>] have been obtained by solution combustion synthesis followed by annealing (<jats:italic>ϑ</jats:italic>= 850°C) at appropriate oxygen pressures. These new phosphates show substitution of W<jats:sup>5+</jats:sup>by either<jats:italic>M</jats:italic><jats:sup>3+</jats:sup><jats:sub>1/3</jats:sub>W<jats:sup>6+</jats:sup><jats:sub>2/3</jats:sub>(<jats:italic>M</jats:italic>: V, Cr, Fe, Mo) or Ti<jats:sup>4+</jats:sup><jats:sub>1/2</jats:sub>W<jats:sup>6+</jats:sup><jats:sub>1/2</jats:sub>. Members of the MPTB structural series with<jats:italic>m</jats:italic>= 2 [e.g. Cr<jats:sup>III</jats:sup><jats:sub>4/3</jats:sub>W<jats:sup>VI</jats:sup><jats:sub>8/3</jats:sub>O<jats:sub>12</jats:sub>(PO<jats:sub>2</jats:sub>)<jats:sub>4</jats:sub>; Ti<jats:sup>IV</jats:sup><jats:sub>6/3</jats:sub>W<jats:sup>VI</jats:sup><jats:sub>6/3</jats:sub>O<jats:sub>12</jats:sub>(PO<jats:sub>2</jats:sub>)<jats:sub>4</jats:sub>] and<jats:italic>m</jats:italic>= 4 [e.g. Cr<jats:sub>4/3</jats:sub>W<jats:sub>20/3</jats:sub>O<jats:sub>24</jats:sub>(PO<jats:sub>2</jats:sub>)<jats:sub>4</jats:sub>] have been obtained. In the course of our investigation the crystal structure of WOPO<jats:sub>4</jats:sub>(MPTB with<jats:italic>m</jats:italic>= 2: W<jats:sub>4</jats:sub>O<jats:sub>12</jats:sub>(PO<jats:sub>2</jats:sub>)<jats:sub>4</jats:sub>) has been re-determined from X-ray single-crystal data, showing monoclinic instead of the orthorhombic symmetry reported in literature (<jats:italic>P</jats:italic>2<jats:sub>1</jats:sub><jats:italic>/m</jats:italic>,<jats:italic>Z</jats:italic>= 1, 80 parameters, 1832 independent reflections<jats:italic>R</jats:italic><jats:sub>1</jats:sub>= 0.027,<jats:italic>wR</jats:italic><jats:sub>2</jats:sub>= 0.063). The crystal structures of Mo<jats:sup>III</jats:sup><jats:sub>4/3</jats:sub>W<jats:sup>VI</jats:sup><jats:sub>8/3</jats:sub>O<jats:sub>12</jats:sub>(PO<jats:sub>2</jats:sub>)<jats:sub>4</jats:sub>and Cr<jats:sup>III</jats:sup><jats:sub>4/3</jats:sub>W<jats:sup>VI</jats:sup><jats:sub>8/3</jats:sub>O<jats:sub>12</jats:sub>(PO<jats:sub>2</jats:sub>)<jats:sub>4</jats:sub>(MPTBs with<jats:italic>m</jats:italic>= 2) were also refined from single-crystal data {(Mo/W (Cr/W):<jats:italic>P</jats:italic>2<jats:sub>1</jats:sub><jats:italic>/m</jats:italic>,<jats:italic>Z</jats:italic>= 1, 80(86) parameters, 1782(1769) independent reflections,<jats:italic>R</jats:italic><jats:sub>1</jats:sub>= 0.035(0.059),<jats:italic>wR</jats:italic><jats:sub>2</jats:sub>= 0.081(0.146)}. These refinements indicate statistical distribution of<jats:italic>M</jats:italic><jats:sup>III</jats:sup>and W<jats:sup>VI</jats:sup>over the metal sites. By selected area electron diffraction the unit cell dimensions of Cr<jats:sup>III</jats:sup><jats:sub>4/3</jats:sub>W<jats:sup>VI</jats:sup><jats:sub>8/3</jats:sub>O<jats:sub>12</jats:sub>(PO<jats:sub>2</jats:sub>)<jats:sub>4</jats:sub>and Cr<jats:sup>III</jats:sup><jats:sub>4/3</jats:sub>W<jats:sup>VI</jats:sup><jats:sub>20/3</jats:sub>O<jats:sub>24</jats:sub>(PO<jats:sub>2</jats:sub>)<jats:sub>4</jats:sub>derived from XRPD and SXRD are confirmed. HRTEM images of Cr<jats:sub>4/3</jats:sub>W<jats:sub>20/3</jats:sub>O<jats:sub>24</jats:sub>(PO<jats:sub>2</jats:sub>)<jats:sub>4</jats:sub>are in agreement with its assumed close structural relation to W<jats:sub>8</jats:sub>O<jats:sub>24</jats:sub>(PO<jats:sub>2</jats:sub>)<jats:sub>4</jats:sub>and show an highly ordered atomic arrangement.</jats:p>

Topics

• Oxygen
• electron diffraction
• combustion
• annealing
• tungsten
• bronze