Synthesis and Characterization of High-Entropy A2B2O7 Pyrochlore with Multiple Elements at A and B Sites

Single nano high -entropy pyrochlore-type compound (A 2 B 2 O 7 ) with 7 different rareearth cations at site A and 3 different metal cations at site B with equiatomic amounts (7A 1/7 ) 2 (3B 1/3 ) 2 O 7 is successfully obtained. The powder with nominal composition (La 1/7 Sm 1/7 Nd 1/7 Pr 1/7 Y 1/7 Gd 1/7 Yb 1/7 ) 2 (Sn 1/3 Hf 1/3 Zr 1/3 ) 2 O 7 was fabricated by reacting metal nitrates (site A) and metal chlorides (site B) with glycine during the combustion reaction. The XRD analysis revealed that the powder attained during synthesis is in an amorphous state. To induce crystallization of the obtained pyrochlore structure, the post -calcination process at 600-1500 o C was conducted and studied. Results of this study showed that the monophase pyrochlore (A 2 B 2 O 7 ) structure is obtained during the calcination at 900 o C. The high -density ceramic pellet with 97% of theoretical density and free of any additives was obtained through pressureless sintering at 1650 o C for 4 h in the air using the powder calcined at 900 o C.