Phase evolution and mechanical properties of novel nanocrystalline Y2(TiZrHfMoV)2O7 high entropy pyrochlore

High entropy pyrochlores (HEP) are potential candidates as dispersoids in the oxide dispersed strengthened steels or alloys, which can be used in nuclear reactors and supercritical boilers. For the first time, HEP oxides Y2(TiZrHfMoV)2O7 were synthesized with Y2Ti2O7 as a base structure with the B site (Ti) substituted with five cations through reverse co-precipitation technique in the nanocrystalline form at lowest synthesis temperature. The synthesis parameters for Y2(TiZrHfMoV)2O7 (5C) and other derived compositions (five compositions of four cationic systems with each cation eliminated at B site from 5C) are optimised to obtain lower crystallite and particle sizes. 5C has a smaller crystallite size (27 nm) than other single-phase compositions. The cation's influence, oxidation state, and oxygen vacancy in the phase formation were analysed through XPS. The single-phase HEPs are consolidated through spark plasma sintering. Y2(TiZrHfMo)2O7 (4C-V) shows the highest hardness among the compositions reported so far due to its finer grain size, and Y2(TiHfMoV)2O7 (4C-Zr) has a higher Young's modulus compared to other single-phase composition due to its higher degree of order in the structure.