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Issue 44, 2017
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On the relations between the bandgap, structure and composition of the M–Si–N (M = alkali, alkaline earth or rare-earth metal) nitridosilicates

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Abstract

Relations between the bandgap and structural properties and composition of the M–Si–N nitridosilicates (M = alkali, alkaline earth or rare earth metal) have been obtained, using experimental data collected from literature; and qualitative models are presented to explain the observed trends. Compounds with a higher degree of condensation, i.e. a higher Si/N ratio, generally have longer M–N bonds and shorter Si–N bonds. The observations can be explained based on the effective charge of N, dependent on its coordination with Si (NSix). With increasing Si/N ratio the coordination number of N by Si increases, making the effective charge of the nitrogen atom less negative, resulting in a longer and less covalent M–N bond. This also shifts the N 2p levels down in energy, lowering the top of the valence band (mainly composed of N orbitals); while decreasing the Si–N distance shifts the bottom of the conduction band (mainly composed of Si and M orbitals) upward. Some nitridosilicates show deviations to the general trends, such as γ-Si3N4 and several Li-containing compounds. These deviations have been discussed and possible explanations have been given based on peculiarities in their structural characteristics.

Graphical abstract: On the relations between the bandgap, structure and composition of the M–Si–N (M = alkali, alkaline earth or rare-earth metal) nitridosilicates

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Publication details

The article was received on 18 Sep 2017, accepted on 16 Oct 2017 and first published on 17 Oct 2017


Article type: Paper
DOI: 10.1039/C7TC04259K
Citation: J. Mater. Chem. C, 2017,5, 11504-11514
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    On the relations between the bandgap, structure and composition of the M–Si–N (M = alkali, alkaline earth or rare-earth metal) nitridosilicates

    O. M. ten Kate, Z. Zhang and H. T. (. Hintzen, J. Mater. Chem. C, 2017, 5, 11504
    DOI: 10.1039/C7TC04259K

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