Structural study on novel two-dimensional superconductor NaxHfNCl

Shamoto, S.; Iizawa, K.; Yamada, Motoko; Ohoyama, Kenji; Yamaguchi, Y.; Kajitani, Tsuyoshi

doi:10.1016/s0022-3697(99)00155-9

Journal of Physics and Chemistry of Solids

1999

DOI: 10.1016/s0022-3697(99)00155-9

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Structural study on novel two-dimensional superconductor NaxHfNCl

S. Shamoto

K. Iizawa

Motoko Yamada

et al.

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Cited by 35 publications

(25 citation statements)

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“…Taking into account the previously published structural data, we should consider that the phase reported by Shamoto et al, 8 Na 0.29 HfNCl, corresponds to a diluted stage 1 intercalate of HfNCl with all of the van der Waals gaps filled with relative occupancy of ca. 50%.…”

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confidence: 94%

“…The resolution achieved in our X-ray diffraction patterns allows the conclusion that all the sodium intercalated samples are a mixture of either the pristine b-HfNCl and a new intermediate phase or the intermediate phase and Na 0.29 HfNCl. 8 We did not obtain any biphasic sample containing only Na 0.29 HfNCl and the pristine. The average interlayer spacings observed for Na 0.29 HfNCl and b-HfNCl are 9.86(4) and 9.24(2) Å respectively whereas the intermediate phase shows a interlayer *amparo.fuertes@icmab.es separation between 9.48 and 9.67 Å depending on the sample.…”

mentioning

confidence: 94%

“…Superconductivity in ZrNX or HfNX is induced by intercalation of alkaline metals or Lewis bases as cobaltocene or pyridine into the van der Waals gap. [1][2][3]5,7 For sodium intercalated hafnium nitride chloride a superconducting phase has been reported with critical temperatures of 20, 23 or 24 K [8][9][10][11] and in lithium intercalated HfNCl, critical temperatures of 18, 20, 24 and 26 K have been observed in different samples showing in some cases co-intercalated organic molecules. 2,12,13 In both systems as well as in doped zirconium nitride chloride that shows lower critical temperatures (close to 12 K), the influence on the critical temperature of factors such as the nature of the transition metal, the co-intercalated molecules and the doping level have still not been completely understood.…”

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confidence: 99%

“…The crystal structure of Na x HfNCl with x 5 0.29 has been reported as isotypic to YOF with space group R3m and crystal parameters a 5 3.5892(3) Å and c 5 29.722(3) Å . 8 The interlayer spacing is 1/3 of the c parameter, being 9.80 Å for Na 0.29 HfNCl and 9.22 Å for the pristine. 3 Staging during intercalation of layered compounds is a phenomenon that has been frequently observed in graphite and in transition metal dichalcogenides, in which a unit consisting of a guest layer followed by n host layers (for a stage-n compound) is repeated along the c axis.…”

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confidence: 99%

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A new intermediate intercalate in superconducting sodium-doped hafnium nitride chloride

et al. 2005

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A new phase has been observed during the sodium intercalation of hafnium nitride chloride as intermediate between the host b-HfNCl and the already reported Na 0.29 HfNCl with T c of 24 K; the new intermediate shows interlayer spacings ranging from 9.48 to 9.67 Å , corresponds to a second stage intercalate of HfNCl and is superconducting with a critical temperature of 20 K.Intercalated zirconium and hafnium nitride halides have been reported to exhibit superconductivity with high critical temperatures within non oxidic compounds. 1,2 The pristine compounds MNX (M 5 Zr, Hf; X 5 Cl, Br, I) show two layered polytypes, a and b phases, isotypic to FeOCl and SmSI respectively. 3,4-6 The structure of the b phase can be described as a stacking along the c axis of double layers with composition [X-M-N-N-M-X], separated by a van der Waals gap. Superconductivity in ZrNX or HfNX is induced by intercalation of alkaline metals or Lewis bases as cobaltocene or pyridine into the van der Waals gap. [1][2][3]5,7 For sodium intercalated hafnium nitride chloride a superconducting phase has been reported with critical temperatures of 20, 23 or 24 K 8-11 and in lithium intercalated HfNCl, critical temperatures of 18, 20, 24 and 26 K have been observed in different samples showing in some cases co-intercalated organic molecules. 2,12,13 In both systems as well as in doped zirconium nitride chloride that shows lower critical temperatures (close to 12 K), the influence on the critical temperature of factors such as the nature of the transition metal, the co-intercalated molecules and the doping level have still not been completely understood. The crystal structure of Na x HfNCl with x 5 0.29 has been reported as isotypic to YOF with space group R3m and crystal parameters a 5 3.5892(3) Å and c 5 29.722(3) Å . 8 The interlayer spacing is 1/3 of the c parameter, being 9.80 Å for Na 0.29 HfNCl and 9.22 Å for the pristine. 3 Staging during intercalation of layered compounds is a phenomenon that has been frequently observed in graphite and in transition metal dichalcogenides, in which a unit consisting of a guest layer followed by n host layers (for a stage-n compound) is repeated along the c axis. 14,15 The phase Na 0.29 HfNCl has been described as a diluted stage 1 intercalate, with all the van der Waals gaps partially filled with sodium atoms. Here we report a new intercalated phase, with interlayer spacing between 9.48 and 9.67 Å that is obtained as an intermediate in the intercalation process of the host to give Na 0.29 HfNCl. The new phase shows a critical temperature of 20 K and can be interpreted as a second stage intercalate of HfNCl.HfNCl or ZrNCl were prepared by reaction of hafnium (Aldrich 99.5%) or zirconium (Alfa 99.9%) and ammonium chloride (Aldrich 99.99%) in the stoichiometric ratio 1:1.1 at temperatures between 740 and 780 uC during 12 hours in sealed evacuated silica tubes. In a second step a temperature gradient of 100 uC was applied to the same reaction tube and HfNCl and ZrNCl were recrystallized by chemical vapour trans...

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confidence: 94%

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confidence: 94%

mentioning

confidence: 99%

mentioning

confidence: 99%

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A new intermediate intercalate in superconducting sodium-doped hafnium nitride chloride

et al. 2005

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“…However, the increase up to T c = 25 K in Na x HfNCl (x ∼ 0.29) [6,7] provides impetus to reevaluate this system, since it became the third highest value of T c outside of the layered cuprate superconductors.…”

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confidence: 99%

Electron doping in the honeycomb bilayer superconductors (Zr, Hf)NCl

Weht¹,

Filippetti²,

Pickett³

1999

Europhys. Lett.

112

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PACS. 74.70Ad -Metals; alloys and binary compounds (including A15, Laves phases, etc.). PACS. 74.25Jb -Electronic structure. PACS. 74.25Kc -Phonons.Abstract. -Based on a virtual crystal treatment, we show that alkali doping introduces electron carriers into a single light mass (m * = 0.6), low density of states band in LixZrNCl and Na xHfNCl (which have superconducting Tc up to 25 K) that is a symmetric interlayer combination of d xy , d x 2 −y 2 character. Doping leads to simple K-centered three-fold symmetrical cylindrical Fermi surfaces that concentrate low-energy scattering into distinct regions of momentum. The lack of any observed magnetic tendencies, together with our calculation of small electron-phonon strength, suggests a pairing mechanism that is distinct from known superconductors.Superconductivity in doped quasi-two-dimensional (2D) compounds has been of intense interest since the discovery of the strong dependence of the critical temperature, T c , on intercalation of the transition metal dichalcogenides [1], and the discovery of high T c in 2D cuprates further heightened their study. The manner in which doping of 2D layers alters their electronic behaviour varies greatly depending on the system. Cuprate high-temperature superconductors, for instance, have a magnetic insulator to metal transition that completely modifies their electronic structure and continues to attract a huge amount of study [2]. In the dichalcogenides there is minimal magnetic behaviour, and carrier doping occurs in a rigid-band fashion. The fulleride superconductors A 3 C 60 (A = alkali) provide another example in which rigid-band doping gives a realistic picture [3] of a relatively high critical temperature (T c ) superconductor.Superconductivity up to 12 K in Li-doped ZrNCl was found by Yamanaka et al. [4] (and extended by Shamoto et al. [5]), suggesting a behaviour related to the dichalcogenides, since T c was in the same range. However, the increase up to T c = 25 K in Na x HfNCl (x ∼ 0.29) [6,7] provides impetus to reevaluate this system, since it became the third highest value of T c outside of the layered cuprate superconductors.In this paper we present several results that we think are very important in furthering the theoretical understanding of this system: 1) for values of doping where the compounds c EDP Sciences

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Electronic band structure of β-ZrNCl-based nanotubes

Enyashin

Makurin²,

Ivanovskiĭ

2004

Chemical Physics Letters

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Structural study on novel two-dimensional superconductor NaxHfNCl

Cited by 35 publications

References 5 publications

A new intermediate intercalate in superconducting sodium-doped hafnium nitride chloride

A new intermediate intercalate in superconducting sodium-doped hafnium nitride chloride

Electron doping in the honeycomb bilayer superconductors (Zr, Hf)NCl

Electronic band structure of β-ZrNCl-based nanotubes

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