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  • Low-temperature phase transition and magnetic properties of ▫${\rm K_3Yb_Si_2O_7}$▫ [Elektronski vir]
    Dabić, Predrag Dabić ...
    The new ambient-temperature hexagonal (space group ▫$P6_3/mmc)$▫ polymorph of tripotassium ytterbium(III) disilicate ▫${\rm (\beta - K_3YbSi_2O_7)}$▫ has been synthesized by the high-temperature flux ... method and subsequently structurally characterized. In the course of the temperature-dependent single-crystal diffraction experiments, a phase transformation of ▫${\rm (\beta - K_3YbSi_2O_7)}$▫ to a novel low-temperature orthorhombic phase ▫${\rm (\beta' - K_3YbSi_2O_7)}$▫, space group ▫$Cmcm$▫) has been observed at about 210 K. ▫${\rm (\beta - K_3YbSi_2O_7)}$▫ is isostructural with ▫${\rm K_3ErSi_2O_7}$▫, whereas ▫${\rm (\beta' - K_3YbSi_2O_7)}$▫ adopts a new type of structure. Both compounds can be built up from a regular alternation of layers of two types, which are parallel to the (001) plane. In the octahedral layer, ▫${\rm YbO_6}$▫ octahedra are isolated and linked by ▫${\rm K1O_{6+3}}$▫ polyhedra. The second, slightly thicker sorosilicate layer is formed by a combination of ▫${\rm Si_2O_7}$▫ dimers and ▫${\rm K2O_{6+3}}$▫ polyhedra. The boundary between the layers is a pseudo-kagome oxide sheet based on 3.6.3.6 meshes. The phase transition is due to a tilt of the two ▫${\rm Si_2O_4}$▫ tetrahedra forming a single dimer which induces a decrease of the ▫${\rm Si - O - Si}$▫ angle between bridging ▫${\rm Si - O}$▫ bonds from 180° (dictated by symmetry in space group ▫$P6_3/mmc)$▫ to ▫$\simeq164^\circ$▫. Magnetic characterization indicates that ▫${\rm K_3YbSi_2O_7)}$▫ remains paramagnetic down to 2 K, showing no apparent influence of the phase transformation on its magnetic properties. Analysis of the magnetization data revealed the positions of the three lowest crystal field levels of the ▫${\rm Yb^{3_+}}$▫ cations, as well as the corresponding projections of their angular momentum on the direction of the magnetic field.
    Vir: Acta crystallographica [Elektronski vir]. Section B, Structural science, crystal engineering and materials. - ISSN 2052-5206 (Vol. B77, part. 4, Aug. 2021, str. 584-593)
    Vrsta gradiva - e-članek ; neleposlovje za odrasle
    Leto - 2021
    Jezik - angleški
    COBISS.SI-ID - 125005059

    Povezava(-e):

    https://scripts.iucr.org/cgi-bin/paper?S2052520621006077
    DOI

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