Sintering and Oxidation of GdB4 Synthesized by B4C Reduction Method

Gadolinium tetraboride (GdB 4 ) was synthesized by reduction of Gd 2 O 3 using boron carbide in presence of carbon. Effect of temperature on product quality was investigated. Pure GdB 4 powder was obtained in vacuum at 1500 o C. Pressureless sintering experiments revealed that sintering takes place only above 1600 o C. A maximum density of 77.1% of the theoretical value was obtained at 1800 o C by pressureless sintering. Hot pressing resulted in 95.5% of theoretical density at the lower temperature of 1700 o C under 35 MPa pressure. Hardness and fracture toughness of dense GdB 4 were measured and found to be 21.4 GPa and 2.3 MPam 1/2 , respectively. After exposure to air at 900 o C, the formation of a porous and non-protective oxide layer was observed.