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Title: Synthesis and characterisation of In-doped MnWO{sub 4}-type solid-solutions: Mn{sub 1−3x}In{sub 2x}□{sub x}WO{sub 4} (x=0–0.11)

Substitution of In{sup 3+} for Mn{sup 2+} in MnWO{sub 4}, which is one of the most studied multiferroics, was conducted systematically by solid-state reactions at 1050 °C to obtain a series of Mn{sub (1−3x)}In{sub 2x}□{sub x}WO{sub 4} solid solutions (x=0–0.11; the box indicates vacancy). The successful In-doping could be proven by electron microprobe, and statically disordered structures of this solid solution series were elucidated by Rietveld analyses with X-Ray powder diffraction (XPD) data. Its average structure maintains the space group P2/c at least up to the replacement of 33 at% Mn. The tendency of their unit cells proportionally enlarging with In-doping is an unexpected observation because In{sup 3+} is smaller than Mn{sup 2+}. This could not be explained alone by average atomic bonding distances and angles evaluated from XPD data analyses. Complimentarily, micro-Raman spectra of Mn{sub (1−3x)}In{sub 2x}□{sub x}WO{sub 4} materials feature a hardening of Raman modes due to stronger atomic bonds in W{sub 2}O{sub 4} and WO{sub 2} units with increasing In-doping. This is considered as an inevitable consequence of broken bonding in directly neighbouring Mn–O bonds as the presence of In{sup 3+} in MnWO{sub 4} accompanies the creation of defects at Mn sites. The current study using XRDmore » and micro-Raman suggests the enlarging local space around the bridging oxygen as the reason for the unexpected cell expansion when smaller In{sup 3+} along with defects replace Mn{sup 2+} in MnWO{sub 4}. - Graphical abstract: Despite of substitution of smaller In{sup 3+} for larger Mn{sup 2+}, the In-rich solid solution Mn{sub 0.71(2)}In{sub 0.19(1)}□{sub 0.10}WO{sub 4} undergoes a volume expansion of 0.4% with respect to MnWO{sub 4}. This could be explained by a local space expansion of 0.13% around bridging oxygen at O2 sites, as illustrated by dashed lines for clarity. - Highlights: • Investigation of Mn{sub (1−3x)}In{sub 2x}□{sub x}WO{sub 4} solid solutions (x=0–0.11). • An unexpected lattice expansion by In-doping. • Strong change in local environment around bridging oxygens. • Enhancement of atomic bonds in W{sub 2}O{sub 4} and WO{sub 2} units with increasing In-doping.« less
Authors:
 [1] ;  [1] ;  [2]
  1. Section Crystallography, Department for Earth and Environmental Sciences, Ludwig-Maximilians-Universität München, Theresienstrasse 41, 80333 Munich (Germany)
  2. Mineralogische Staatssammlung München, Theresienstrasse 41, 80333 Munich (Germany)
Publication Date:
OSTI Identifier:
22443459
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Solid State Chemistry; Journal Volume: 219; Other Information: Copyright (c) 2014 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; BONDING; DATA ANALYSIS; DOPED MATERIALS; ELECTRON MICROPROBE ANALYSIS; HARDENING; MANGANESE TUNGSTATES; MONOCLINIC LATTICES; OXYGEN; RAMAN SPECTRA; RAMAN SPECTROSCOPY; SOLID SOLUTIONS; SOLIDS; SPACE GROUPS; SYNTHESIS; TUNGSTEN OXIDES; X-RAY DIFFRACTION; X-RAY PHOTOELECTRON SPECTROSCOPY