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Thermal stability, morphology and electronic band gap of Zn(NCN)

Morita, Koji and Mera, Gabriela and Yoshida, Kaname and Ikuhara, Yuichi and Klein, Andreas and Kleebe, Hans-Joachim and Riedel, Ralf (2013):
Thermal stability, morphology and electronic band gap of Zn(NCN).
In: Solid State Sciences, Elsevier Science Publishing, pp. 50-57, 23, ISSN 12932558,
[Online-Edition: http://dx.doi.org/10.1016/j.solidstatesciences.2013.06.008],
[Article]

Abstract

The thermal behavior of zinc carbodiimide Zn(NCN) was examined in the temperature range between 200 and 1100 °C in Ar atmosphere. The material starts to partially decompose at about 800 °C. Heat treatment at temperatures beyond 800 °C results in the formation of the byproducts nitrogen-containing bamboo-like multiwall carbon-nanotubes of 20–50 nm in diameter due to a partial decomposition of Zn(NCN) into dicyan (CN)2, zinc and nitrogen gas followed by the polymerization of the former product to paracyanogen (CN)n. At 1100 °C, the yield of the residual carbodiimide depends on the dwelling time and the initial amount of powder used for pyrolysis. One hour dwelling at 1100 °C yields ∼50% of the Zn(NCN) separated as pure material. Temperature-induced change in the band structure, namely indirect-to-direct band gap transition, is registered when compared the Zn(NCN) at room temperature with the residual material annealed at 1100 °C. The transition from indirect (Eg = 4.32 eV) to direct band gap (Eg = 4.93 eV) is due to the thermal annealing process which results in healing of crystal defects.

Item Type: Article
Erschienen: 2013
Creators: Morita, Koji and Mera, Gabriela and Yoshida, Kaname and Ikuhara, Yuichi and Klein, Andreas and Kleebe, Hans-Joachim and Riedel, Ralf
Title: Thermal stability, morphology and electronic band gap of Zn(NCN)
Language: English
Abstract:

The thermal behavior of zinc carbodiimide Zn(NCN) was examined in the temperature range between 200 and 1100 °C in Ar atmosphere. The material starts to partially decompose at about 800 °C. Heat treatment at temperatures beyond 800 °C results in the formation of the byproducts nitrogen-containing bamboo-like multiwall carbon-nanotubes of 20–50 nm in diameter due to a partial decomposition of Zn(NCN) into dicyan (CN)2, zinc and nitrogen gas followed by the polymerization of the former product to paracyanogen (CN)n. At 1100 °C, the yield of the residual carbodiimide depends on the dwelling time and the initial amount of powder used for pyrolysis. One hour dwelling at 1100 °C yields ∼50% of the Zn(NCN) separated as pure material. Temperature-induced change in the band structure, namely indirect-to-direct band gap transition, is registered when compared the Zn(NCN) at room temperature with the residual material annealed at 1100 °C. The transition from indirect (Eg = 4.32 eV) to direct band gap (Eg = 4.93 eV) is due to the thermal annealing process which results in healing of crystal defects.

Journal or Publication Title: Solid State Sciences
Volume: 23
Publisher: Elsevier Science Publishing
Uncontrolled Keywords: Zinc carbodiimide, Thermal transformation, CNTs, TEM, Band gap
Divisions: 11 Department of Materials and Earth Sciences > Earth Science > Geo-Material-Science
11 Department of Materials and Earth Sciences > Material Science > Dispersive Solids
11 Department of Materials and Earth Sciences > Material Science > Surface Science
11 Department of Materials and Earth Sciences > Earth Science
11 Department of Materials and Earth Sciences > Material Science
11 Department of Materials and Earth Sciences
Date Deposited: 20 Feb 2014 13:24
Official URL: http://dx.doi.org/10.1016/j.solidstatesciences.2013.06.008
Identification Number: doi:10.1016/j.solidstatesciences.2013.06.008
Funders: Financial support by the grants funded under the LOEWE-Zentrum AdRIA (Adaptronik-Research, Innovation, Application), funded by the state of Hesse, Germany and the Fonds der Chemischen Industrie, Frankfurt (Germany) is gratefully acknowledged.
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