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Hydrothermal synthesis, characterization and magnetic properties of three isostructural chain borophosphates; NH4M(III)[BP2O8(OH)] with M=V or Fe and NH4(Fe(III)0.53V(III)0.47)[BP2O8(OH)]

Solid State Sciences
Publication Date
DOI: 10.1016/s1293-2558(01)01182-7
  • Borophosphate
  • Hydrothermal
  • Crystal Structure
  • Antiferromagnetic Ordering
  • Earth Science
  • Geography
  • Physics


Abstract The borophosphates (NH 4)M(III)[BP 2O 8(OH)] with M = V and Fe ( 1 , 2 ) and (NH 4)(Fe(III) 0.53V(III) 0.47)[BP 2O 8(OH)] ( 3) have been synthesized under hydrothermal conditions. In addition, the known compound CsFe(III)[BP 2O 8(OH)] ( 4) has also been synthesized in order to compare its magnetic properties with those obtained for 1, 2 and 3. These four metal borophosphates are isostructural and have infinite anionic [BP 2O 8(OH)] 4 n− n chains as characteristic structural building blocks. The octahedrally coordinated transition metal M(III) ions connect the chains to each other. Hydrogen bonds in the range of 2.89 to 2.97 Å are present between NH + 4 cations and the anionic chains in 1, 2 and 3. Single crystal X-ray diffraction, SEM-EDS analyses, TG/DSC analyses, variable–temperature magnetic susceptibility measurements and FT-IR spectroscopy were used for characterization. Crystal data: Compounds 1, 2, and 3 crystallize in the monoclinic space group P2 1/c, with Z=4. Unit cell parameters; for 1: a=9.425(2) Å, b=8.269(2) Å, c=9.697(3) Å, β=102.26(2)°, V=738.5(2) Å 3, for 2: a=9.393(3) Å, b=8.285(2) Å, c=9.689(2) Å, β=102.07(2)°, V=737.4(4) Å 3, for 3: a=9.404(4) Å, b=8.316(5) Å, c=9.706(2) Å, β=102.28(4)°, V=741.6(5) Å 3. TG data for 1 gave an observed weight loss of 12% which corresponds well to the release of 1 H 2O and 1 NH 3 molecule. For 1 and 4, a continuous decrease of χ M T at low temperatures indicates a possible antiferromagnetic ordering. Maxima in the magnetic susceptibility data were observed for iron borophosphates 2 and 4.

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