Synthesis and structural study of a new group of trigermanates, CaRE₂Ge₃O₁₀(RE = La–Yb)

Abstract

A new series of germanates CaRE 2 Ge 3 O 10 (RE = Y, La-Yb) has been prepared using an EDTA-assisted route.Rietveld refinement of room temperature powder X-ray diffraction patterns shows that these compounds crystallize in the monoclinic system (S.G. P2 1 /c, Z = 4) and have two morphotropic transitions. The calcium and rare earth atoms are distributed among three nonequivalent sites and form layers along the [0 0 1] direction connected into the framework through ijGe 3 O 10 ]. The morphotropic transitions are accompanied by changes in the site occupancy factors of metal cations and by variation in the first and second coordination spheres of Ca 2+ /RE 3+ . CrystEngComm This journal isRussia † Electronic supplementary information (ESI) available: Details of Rietveld refinement of room temperature powder X-ray diffraction patterns (Fig. S1-S12), atomic coordinates, isotropic thermal parameters and Ca 2+ -RE 3+ fractions in the structures of CaRE 2 Ge 3 O 10 ; RE = Y, La-Yb (Tables S1-S4). See

Structural, electronic and optical properties of BaRE6(Ge2O7)2(Ge3O10) (RE = Tm, Yb, Lu) compounds and BaYb6(Ge2O7)2(Ge3O10):Tm3+ and BaLu6(Ge2O7)2(Ge3O10):Yb3+,Tm3+ phosphors: potential applications in temperature sensing

“…3. In the previous publications 35,36 S3, ESI †), is related to the asymmetric stretching bridge vibrations Ge-O-Ge. The most intense line at 834 cm −1 with a shoulder (860 cm −1 ) in the Raman spectrum refers to the symmetric stretching vibrations Ge-O.…”

“…35 In most cases, it is distorted and asymmetric, as, for example, in the structures of CaRE 2 Ge 3 O 10 (RE = Y, La-Yb), Ag 8 Ge 3 O 10 , and Ca 4 (Ge 3 O 10 )•H 2 O. [36][37][38] However, for a number of compounds, including BaRE 2 Ge 3 O 10 (RE = Y, Sc, Gd-Lu), K 2 B 2 Ge 3 O 10 , Rb 2 Ga 2 Ge 3 O 10 , and Ca 7.96 Cu 0.04 Ge 5 O 18 , the presence of a 2-fold rotation axis or mirror plane, residing on the central germanium atom of the [Ge 3 O 10 ] group, has been reported. 35,[39][40][41] The [Ge 2).…”

Ge-Containing Oxide-Ion Conductors with CaEu2Ge3O10-Type Structure Discovered by the Bond-Valence Method and Experiments

“…The refined parameters were consistent with those obtained from the SCXRD analyses. The lattice parameters and occupancy factors of the Ca atom at the three Ca/Sm i ( i = 1, 2, 3) sites, g (Ca; Ca/Sm i ), in CaSm 2 Ge 3 O 10 are consistent with those in Ca R 2 Ge 3 O 10 ( R = Pr, Nd, Eu, Gd, Tb, Dy, Y, Ho, Er, Tm, and Yb), which were reported by Yamane et al and Lipina et al (Figure S10 in the SI). − The occupancy factors of the Ca atom at the three Ca/ Ri ( i = 1, 2, 3) sites become closer by increasing the ionic radius of the rare earth cation from R = Yb to Nd (Figure S10f in the SI). This can be explained by the decrease of the size mismatch between R 3+ and Ca 2+ cations from R = Yb to Nd, giving a more disordered state.…”

“…The first aim of this work is to explore good candidates of oxide-ion conductors from Ge-containing metal oxides (624 compounds) using the bond-valence method. − As described below, we found the CaEu 2 Ge 3 O 10 -type structure as a good candidate of a new structure family of oxide-ion conductors. CaEu 2 Ge 3 O 10 -type CaY 2 Ge 3 O 10 was first reported by Yamane et al, and its luminescence properties were investigated by Lipina et al , Then, Lipina et al systematically investigated crystal structures of Ca R 2 Ge 3 O 10 series ( R : rare earths) . Trisilicates and trigernamates AR 2 T 3 O 10 ( A : Ca, Co, Sr, Ba; T : Si, Ge) attract interest because of their possible applications as optical materials. − …”

“…CaEu 2 Ge 3 O 10 -type CaY 2 Ge 3 O 10 was first reported by Yamane et al, 46 and its luminescence properties were investigated by Lipina et al 47,48 Then, Lipina et al systematically investigated crystal structures of CaR 2 Ge 3 O 10 series (R: rare earths). 49 Trisilicates and trigernamates AR 2 T 3 O 10 (A: Ca, Co, Sr, Ba; T: Si, Ge) attract interest because of their possible applications as optical materials. 50−52 In the present work, (i) we synthesized CaGd 2 Ge 3 O 10 , CaEu 2 Ge 3 O 10 , and Ca 1+x Sm 2−x Ge 3 O 10−x/2 (x = 0, 0.05, 0.1 and 0.2) and (ii) their electrical conductivities were measured.…”