Discovery of Ternary Silicon Titanium Nitride with Spinel-Type Structure

Abstract : Here we report on the discovery of a ternary silicon titanium nitride with the general composition (Si 1−x ,ti x) 3 n 4 with x = 0 < x < 1 and spinel-type crystal structure. The novel nitride is formed from an amorphous silicon titanium nitride (Sitin) precursor under high-pressure/high-temperature conditions in a large volume high-pressure device. Under the conditions of 15-20 GPa and 1800-2000 °C, spineltype γ-Si 3 n 4 and rock salt-type c-TiN are formed. In addition, crystals of the discovered nano-sized ternary phase (Si 1−x ,ti x) 3 n 4 embedded in γ-Si 3 n 4 are identified. The ternary compound is formed due to kinetically-controlled synthesis conditions and is analyzed to exhibit the spinel-type structure with ca. 8 atom% of Ti. The Ti atoms occur in both Ti 3+ and ti 4+ oxidation states and are located on the Si sites. the ternary nano-crystals have to be described as (Si,ti) 3 n 4 with n-vacancies resulting in the general composition (Si 4+ 1−x ti 4+ x-δ ti 3+ δ) 3 n 4-δ .