High-pressure synthesis of predicted oxynitride perovskite: Yttrium Silicon Oxynitride (YSiO$_{2}$N)

We synthesized the previously predicted [1] polar oxynitride perovskite in a diamond anvil cell with laser heating. YSiO$_{2}$N was predicted to have the polar $P$4mm structure with an effective spontaneous polarization of 130 $\mu $C/cm$^{2}$. A mixture of Yttrium nitride (YN) and amorphous Silicon dioxide (SiO$_{2})$ were loaded into a diamond anvil cell and laser heated at or above 1200 C at 12 GPa. The run products were investigated by x-ray diffraction, Raman spectroscopy, and second harmonic generation, for their phase and structural properties. The x-ray diffraction pattern (a $=$ 3.235 {\AA}, c $=$ 4.485 {\AA}) shows the phase formation of YSiO$_{2}$N and matches with the diffraction pattern derived from the first-principle predicted lattice parameters. However, minor unknown peaks are on the diffraction pattern indicating of the co-existence of other unknown phases. Further study of Raman spectroscopy observes the theoretically predicted modes, and second harmonic generation shows strong non-linear optical signal, which confirms the polar properties of YSiO$_{2}$N. [1] R. Caracas and R. E. Cohen, Appl. Phys. Lett. 91, 092902 (2007).