Ion exchange synthesizes layered polymorphs of MgZrN$_2$ and MgHfN$_2$, two metastable semiconductors
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| Format: | Preprint |
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2024
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| _version_ | 1866909748382662656 |
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| author | Rom, Christopher L. Jankousky, Matthew Phan, Maxwell Q. O'Donnell, Shaun Regier, Corlyn Neilson, James R. Stevanovic, Vladan Zakutayev, Andriy |
| author_facet | Rom, Christopher L. Jankousky, Matthew Phan, Maxwell Q. O'Donnell, Shaun Regier, Corlyn Neilson, James R. Stevanovic, Vladan Zakutayev, Andriy |
| contents | The synthesis of ternary nitrides is uniquely difficult, in large part because elemental N$_2$ is relatively inert. However, lithium reacts readily with other metals and N$_2$, making Li-M-N the most numerous sub-set of ternary nitrides. Here, we use Li$_2$ZrN$_2$, a ternary with a simple synthesis recipe, as a precursor for ion exchange reactions towards AZrN$_2$ (A = Mg, Fe, Cu, Zn). In situ synchrotron powder X-ray diffraction studies show that Li$^+$ and Mg$^{2+}$ undergo ion exchange topochemically, preserving the layers of octahedral [ZrN$_6$] to yield a metastable layered polymorph of MgZrN$_2$ (spacegroup $R\overline{3}m$) rather than the calculated ground state structure ($I41/amd$). UV-vis measurements show an optical absorption onset near 2.0 eV, consistent with the calculated bandgap for this polymorph. Our experimental attempts to extend this ion exchange method towards FeZrN$_2$, CuZrN$_2$, and ZnZrN$_2$ resulted in decomposition products (A + ZrN + 1/6 N$_2$), an outcome that our computational results explain via the higher metastability of these phases. We successfully extended this ion exchange method to other Li-M-N precursors by synthesizing MgHfN$_2$ from Li$_2$HfN$_2$. In addition to the discovery of metastable $R\overline{3}m$ MgZrN$_2$ and MgHfN$_2$, this work highlights the potential of the 63 unique Li-M-N phases as precursors to synthesize new ternary nitrides. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2412_02600 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Ion exchange synthesizes layered polymorphs of MgZrN$_2$ and MgHfN$_2$, two metastable semiconductors Rom, Christopher L. Jankousky, Matthew Phan, Maxwell Q. O'Donnell, Shaun Regier, Corlyn Neilson, James R. Stevanovic, Vladan Zakutayev, Andriy Materials Science The synthesis of ternary nitrides is uniquely difficult, in large part because elemental N$_2$ is relatively inert. However, lithium reacts readily with other metals and N$_2$, making Li-M-N the most numerous sub-set of ternary nitrides. Here, we use Li$_2$ZrN$_2$, a ternary with a simple synthesis recipe, as a precursor for ion exchange reactions towards AZrN$_2$ (A = Mg, Fe, Cu, Zn). In situ synchrotron powder X-ray diffraction studies show that Li$^+$ and Mg$^{2+}$ undergo ion exchange topochemically, preserving the layers of octahedral [ZrN$_6$] to yield a metastable layered polymorph of MgZrN$_2$ (spacegroup $R\overline{3}m$) rather than the calculated ground state structure ($I41/amd$). UV-vis measurements show an optical absorption onset near 2.0 eV, consistent with the calculated bandgap for this polymorph. Our experimental attempts to extend this ion exchange method towards FeZrN$_2$, CuZrN$_2$, and ZnZrN$_2$ resulted in decomposition products (A + ZrN + 1/6 N$_2$), an outcome that our computational results explain via the higher metastability of these phases. We successfully extended this ion exchange method to other Li-M-N precursors by synthesizing MgHfN$_2$ from Li$_2$HfN$_2$. In addition to the discovery of metastable $R\overline{3}m$ MgZrN$_2$ and MgHfN$_2$, this work highlights the potential of the 63 unique Li-M-N phases as precursors to synthesize new ternary nitrides. |
| title | Ion exchange synthesizes layered polymorphs of MgZrN$_2$ and MgHfN$_2$, two metastable semiconductors |
| topic | Materials Science |
| url | https://arxiv.org/abs/2412.02600 |