Holmium polysulfides: crystal growth, structure and properties

• Published in: Journal of alloys and compounds Vol. 323; pp. 26 - 33
• Main Authors: Belaya, S.V, Vasilyeva, I.G, Pervukhina, N.V, Podberezskaya, N.V, Eliseev, A.P
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 12.07.2001
• Subjects: Crystal growth; Holmium polysulfides; Optical properties; Structure; Crystal growth; Structure; Optical properties; Holmium polysulfides
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/S0925-8388(01)01002-7

Crystals of holmium polysulfides, up to 3×2×1.5 mm in size, were grown by spontaneous crystallization from melted KI. A diversity in morphology was observed from thin transparent plates to polyhedrons with mirror-like surfaces. For crystals of different forms, the composition was determined, and density as well as refractory index was measured. Several phases crystallized, two of which were characterized using single-crystal X-ray diffraction as HoS 1.885(5) (I), tetragonal, P4/ nmm, a=3.820(1), c=7.840(3) Å, V=114.40(6) Å 3, Z=2, d cal=6.542 g/cm 3 and HoS 1.863(8) (II), monoclinic P2 1/ m, a=10.961(2), b=11.465(2), c=10.984(2) Å, β=91.27(3)°, V=1380.0(4) Å 3, Z=24, d cal=6.486 g/cm 3. Raman spectra reveals the characteristic band, corresponding to S −–S − pair vibrations in the polyanionic layer. Crystals are transparent in the 0.65–25 μm spectral range, the bands with a fine structure in the transparency region being related to Ho 3+. The shortwave absorption edge is described by an exponential law (Urbach’s rule) due to tails of state density for conduction and valence bands.