Abstract
Here we report on the discovery of a ternary silicon titanium nitride with the general composition (Si1−x,Tix)3N4 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-Si3N4 and rock salt-type c-TiN are formed. In addition, crystals of the discovered nano-sized ternary phase (Si1−x,Tix)3N4 embedded in γ-Si3N4 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 Ti3+ and Ti4+ oxidation states and are located on the Si sites. The ternary nano-crystals have to be described as (Si,Ti)3N4 with N-vacancies resulting in the general composition (Si4+1−x Ti4+x-δTi3+δ)3N4-δ.
Highlights
Spinel-type silicon nitride γ-Si3N4 is a high-pressure phase of silicon nitride and has been discovered in 19991
We report on a discovery of a ternary nitride formed between Si3N4 and Ti3N4 synthesized under high-pressure/temperature conditions, namely at pressures of 15–20 GPa and temperatures of 1800– 2000 °C in a large volume press
In our study we first synthesized a single-source precursor (SSP) by the reaction of perhydropolysilazane (PHPS) with tetrakis(dimethylamido)titanium (TDMAT) according to the scheme given in Fig. 2 19,20
Summary
Spinel-type silicon nitride γ-Si3N4 is a high-pressure phase of silicon nitride and has been discovered in 19991. According to their calculations, 39 spinel-type nitrides are characterized by interesting functional and structural features ranging from super-hardness via semiconducting to metallic properties[5]. Experimental studies verified that spinel nitride γ-Si3N4 in particular, and the transition metal nitrides M3N4 with M = Zr, Hf combine ultra-high hardness with high thermal stability against decomposition in different environments. This suggests their promising use in potential applications such as cutting tools[7,8,9]. The ternary (Si,Ti)3N4 crystals are nano-sized and are embedded in γ-Si3N4 single crystals
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