Pentaeuropium dicadmium pentaantimonide oxide, Eu5Cd2Sb5O

Saparov, Bayrammurad; Bobev, Svilen

doi:10.1107/s1600536811000274

Cited by 6 publications

(6 citation statements)

References 11 publications

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“…A brief exposure to the atmosphere during the sealing of an ampoule or inadvertent reduction of alumina (crucible material) might be all the opportunity necessary for unintended oxygen to find its way into the reaction materials or products, resulting in an unplanned oxide phase. While they are infrequent discoveries in our lab, these uncommon oxygen-stabilized phases have been documented in several previous studies, such as Ca 4 Bi 2 O, Ba 2 Cd 3-δ Bi 3 O, Ba 5 Cd 2 Sb 5 O x (0.5 < x < 0.7), Eu 5 Cd 2 Sb 5 O, and Ba 5 Cd 2 Sb 4 O 2 [22][23][24][25][26]. This small group is expanded with the two title compounds presented herein.…”

Section: Introductionmentioning

confidence: 59%

“…63, Pearson symbol oC52), with a crystal structure that contains four unique europium positions, one unique zinc/cadmium position, three unique arsenic positions, and one unique oxygen position in the asymmetric unit (Tables 1 and 2). They adopt the Ba 2 Cd 2 Sb 5 F structure type, which until now included only five compounds: A 5 Cd 2 Sb 5 F (A = Ba, Sr, Eu), Eu 5 Cd 2 Sb 5 O, and Ba 5 Cd 2 Sb 5 O x (x ≈ 0.5-0.7) [24,25]. Interestingly, Eu 5 Zn 2 As 5 O is the first Zn-bearing compound in this small but growing family of compounds, whereas Eu 5 Cd 2 As 5 O is chronologically regarded as the first arsenide of this structure type.…”

Section: Structure Descriptionmentioning

confidence: 99%

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On the New Oxyarsenides Eu5Zn2As5O and Eu5Cd2As5O

2020

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The new quaternary phases Eu5Zn2As5O and Eu5Cd2As5O have been synthesized by metal flux reactions and their structures have been established through single-crystal X-ray diffraction. Both compounds crystallize in the centrosymmetric space group Cmcm (No. 63, Z = 4; Pearson symbol oC52), with unit cell parameters a = 4.3457(11) Å, b = 20.897(5) Å, c = 13.571(3) Å; and a = 4.4597(9) Å, b = 21.112(4) Å, c = 13.848(3) Å, for Eu5Zn2As5O and Eu5Cd2As5O, respectively. The crystal structures include one-dimensional double-strands of corner-shared MAs4 tetrahedra (M = Zn, Cd) and As–As bonds that connect the tetrahedra to form pentagonal channels. Four of the five Eu atoms fill the space between the pentagonal channels and one Eu atom is contained within the channels. An isolated oxide anion O2– is located in a tetrahedral hole formed by four Eu cations. Applying the valence rules and the Zintl concept to rationalize the chemical bonding in Eu5M2As5O (M = Zn, Cd) reveals that the valence electrons can be counted as follows: 5 × [Eu2+] + 2 × [M2+] + 3 × [As3–] + 2 × [As2–] + O2–, which suggests an electron-deficient configuration. The presumed h+ hole is confirmed by electronic band structure calculations, where a fully optimized bonding will be attained if an additional valence electron is added to move the Fermi level up to a narrow band gap (Eu5Zn2As5O) or pseudo-gap (Eu5Cd2As5O). In order to achieve such a formal charge balance, and hence, narrow-gap semiconducting behavior in Eu5M2As5O (M = Zn, Cd), europium is theorized to be in a mixed-valent Eu2+/ Eu3+ state.

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Section: Introductionmentioning

confidence: 59%

Section: Structure Descriptionmentioning

confidence: 99%

On the New Oxyarsenides Eu5Zn2As5O and Eu5Cd2As5O

2020

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“…However, the exact source of oxygen remains unidentified. In prior works, the serendipitous formation of pnictide oxides has been observed, for example in the cases of AE 5 M 2 As 5 O (AE = Ba, Eu; M = Zn, Cd; Pn = As, Sb), 1,34,53,54 process with the rare-earth metal. 57 However, experiments conducted in Nb and BN crucibles under identical conditions also yielded title oxypnictides, dismissing the possibility that alumina crucibles act as the oxygen source.…”

Section: Resultsmentioning

confidence: 97%

“…However, the exact source of oxygen remains unidentified. In prior works, the serendipitous formation of pnictide oxides has been observed, for example in the cases of AE 5 M 2 As 5 O ( AE = Ba, Eu; M = Zn, Cd; Pn = As, Sb), ,,, U 2 Cu 2 As 3 O, and Ba 5 Cd 2 Sb 4 O 2 , to name a few. Our initial hypothesis was based on the reported studies, where alumina crucibles are the oxygen source via a reduction process with the rare-earth metal .…”

Section: Resultsmentioning

confidence: 98%

Advancing Heteroanionicity in Zintl Phases: Crystal Structures, Thermoelectric and Magnetic Properties of Two Quaternary Semiconducting Arsenide Oxides, Eu₈Zn₂As₆O and Eu₁₄Zn₅As₁₂O

Ishtiyak,

Watts,

Thipe

et al. 2024

Inorg. Chem.

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Two novel quaternary oxyarsenides, Eu 8 Zn 2 As 6 O and Eu 14 Zn 5 As 12 O, were synthesized through metal flux reactions, and their crystal structures were established by single-crystal X-ray diffraction methods. Eu 8 Zn 2 As 6 O crystallizes in the orthorhombic space group Pbca, featuring polyanionic ribbons composed of corner-shared triangular [ZnAs 3 ] units, running along the [100] direction. The structure of Eu 14 Zn 5 As 12 O crystallizes in the monoclinic space group P2/m and its anionic substructure can be described as an infinite "ribbonlike" chain comprised of [ZnAs 3 ] trigonal-planar units, although the structural complexity here is greater and also amplified by disorder on multiple crystallographic positions. In both structures, the O 2− anion occupies an octahedral void with six neighboring Eu 2+ cations. Formal electron counting, electronic structure calculations, and transport properties reveal the charge-balanced semiconducting nature of these heteroanionic Zintl phases. High-temperature thermoelectric transport properties measurements on Eu 14 Zn 5 As 12 O reveal relatively high resistivity (ρ 500K = 8 Ω•cm) and Seebeck coefficient values (S 500K = 220 μV K −1 ), along with a low concentration and mobility of holes as the dominant charge-carriers (n 500K = 8.0 × 10 17 cm −3 , μ 500K = 6.4 cm 2 /V s). Magnetic studies indicate the presence of divalent Eu 2+ species in Eu 14 Zn 5 As 12 O and complex magnetic ordering, with two transitions observed at T 1 = 21.6 K and T 2 = 9 K.

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“…Over the past seven years, our research group has systematically explored the alkaline-earth metal and rare-earth metal antimonide systems. The resulting new compounds have often been Zintl phases [4][5][6] with complex crystal and electronic structures, and unusual properties [7][8][9][10][11][12][13][14][15][16][17][18][19][20]. Although oxide research is not our focus, it is sometimes the case that adventurous oxygen molecules find their way into our experiments and OPEN ACCESS surprise us with an atypical compound, such as the previously reported Ba 5 Cd 2 Sb 5 O x (0.5 < x < 0.7) [17].…”

Section: Introductionmentioning

confidence: 94%