As a kind of ultra-high temperature ceramics, transition metal borides have the advantages of high melting point, high hardness, excellent high temperature stability, corrosion resistance and high temperature creep resistance. It has great potential in the application of aerospace engine, supersonic vehicle, furnace parts and other harsh environment. However, transition metal borides are difficult to be sintered and densified due to their strong covalent bond and low diffusion coefficient. The preparation of dense pure phase transition metal borides often requires high temperature and pressure conditions, but high temperature often leads to grain coarsening and decreases the mechanical properties of the ceramics. Therefore, in order to promote the densification of transition metal borides, many scholars often increase the sintering driving force by adding sintering additives. For example, Sciti et al successfully prepared 100%ZrB2 ceramics with density at 1700℃/100 MPa by adding 9vol%MoSi2 and SPS. But the presence of glass phase MoSi2 may reduce its inherent mechanical strength and high temperature performance. In addition, reducing the particle size and improving the surface energy of powders is a way to increase the sintering activity of powders and prepare dense boride ceramics. In addition, the uniformity of ceramics also affects its performance to some extent. When the external magnetic field is zero, the temperature of the superconducting material from normal to superconducting state (or vice versa) is represented by Tc, and the magnetic field strength required to change the superconducting state of the superconducting material to normal is destroyed by Hc. At atmospheric pressure, there are 28 elements with superconductivity. The Tc of Niobium (Nb) is up to 9.26K. The superconducting element is added with some other elements as alloy components, which can improve the overall performance of the superconducting material.
For example, the first Niobium zirconium alloy (Nb-75Zr) has a Tc of 10.8K and Hc of 8.7 tert. This was followed by niobium titanium alloys, where although the Tc is slightly lower, the Hc is much higher and can carry more current in a given magnetic field. The properties of ternary alloy are further improved. The Tc=9.9K and Hc=12.4 te (4.2K) of Nb-60Ti-4Ta are obtained. Tc=9.8K and Hc= 12.8th for Nb-70Ti-5Ta. The segregation of solid solution NbB2 in high entropy ceramics was previously reported. Due to insufficient sintering temperature or holding time, the diffusion of NbB2 is slow, so the homogeneous ternary boride ceramics containing NbB2 are expected to have better performance.
Conductive ceramics of Hafnium niobium - based ternary solid solution boride, the molecular formula of the conductive ceramics is (HfaNbbMec)B2, where 0.1≤a≤0.9, 0
