Discovery of Ternary Silicon Titanium Nitride with Spinel-Type Structure

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, spinel-type 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).