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Structure, magnetic and optical properties of Sr3RE2(Ge3O9)2 cyclogermanates (RE = La–Gd)

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Abstract

A new series of Sr3RE2(Ge3O9)2 (RE = La, Pr, Nd, Sm, Eu, Gd) cyclogermanates has been prepared using an ethylenediaminetetraacetic acid assisted route. The powder XRD study reveals that the compounds crystallize in the monoclinic space group C2/c, Z = 4. A decrease in the crystal radius of RE3+ ions in Sr3RE2(Ge3O9)2 (RE = La–Gd) causes a morphotropic phase transition followed by a step-like change of the lattice parameters. The transition is accompanied by internal reorganization, including the redistribution of rare earth and strontium ions among three symmetry independent Sr/RE sites, a conformation change of [Ge3O9]6− rings and a variation of Sr/RE(2) atom coordination from seven-fold to nine-fold. Density functional theory calculations reveal that Sr3RE2(Ge3O9)2 compounds are indirect bandgap materials with a band gap around 3.0 eV. The magnetic property measurements indicate that Sr3RE2(Ge3O9)2 (RE = Pr, Sm, Gd) are Curie–Weiss paramagnets up to 2 K. For Sr3Eu2(Ge3O9)2 an anomaly of magnetic susceptibility is found at about 60 K. A photoluminescence study of the Sr3Sm2(Ge3O9)2 and Sr3Eu2(Ge3O9)2 samples reveals an emission in the visible spectral range, corresponding to the characteristic 4f–4f transitions in rare earth ions.

Graphical abstract: Structure, magnetic and optical properties of Sr3RE2(Ge3O9)2 cyclogermanates (RE = La–Gd)

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Publication details

The article was received on 02 Jan 2018, accepted on 03 Apr 2018 and first published on 12 Apr 2018


Article type: Paper
DOI: 10.1039/C8CE00005K
Citation: CrystEngComm, 2018, Advance Article
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    Structure, magnetic and optical properties of Sr3RE2(Ge3O9)2 cyclogermanates (RE = La–Gd)

    A. Yu. Chufarov, O. A. Lipina, L. L. Surat, M. A. Melkozerova, Y. V. Baklanova, A. N. Enyashin, A. P. Tyutyunnik, D. G. Kellerman and V. G. Zubkov, CrystEngComm, 2018, Advance Article , DOI: 10.1039/C8CE00005K

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