Prediction And Synthesis Of Novel Ti3_B2N Ternary Compound

Predicting and synthesizing new materials can not only enrich material databases,but also meet the increasing demands in industry.Due to the expensive calculation time,structural predictions for ternary phases now have not extensively adopted,especially in the varying-composition searches.During the varying composition search for stable phases in Ti-B-N system,we focused on the compositions between two stable known structures.Meanwhile,the known structures in the Ti-B-N system were added as seeds.With the combining of structural evolutionary algorithm and first-principle calculations,a stable ternary Ti₃B₂N phase has been found,which has similar bonding characters with TiN and TiB₂.The mechanical and electronic properties of the obtained Ti₃B₂N phase were calculated by first-principles methods.By calculating the elastic constants of the Ti-₃B₂N,its bulk modulus,shear modulus and Vicker's hardness were calculated to be 229.6,181.0 and 28.7 GPa,respectively.The tensile and shear strength of Ti₃B₂N were calculated to be 26.3 GPa and 30.5 GPa from the calculated stress-strain relations.The Ti-N bond along the c-direction is found to be the weakest in the Ti₃B₂N structure.The Ti3B2N phase was predicted to be a conductor by analyzing the calculated band structure and density of state,and its conductivity is mainly from the Ti-d electrons.According to the temperature range of stability obtained by calculations,the Ti₃B₂N compound was synthesized successfully at 1200-1400?by high-temperature solid reactions.The impurity TiB₂ in the obtained sample was removed successfully by nitric acid?HNO₃?solution.X-ray diffraction?XRD?results show the crystal structure of the synthesized Ti₃B₂N agrees well with the predicted results.And the crystal structure of Ti₃B₂N was observed by high-resolution scanning transmission electron microscopy?HRSTEM?.