Phase structure evolution and thermal expansion variation of Sc2O3 doped Nd2Zr2O7 ceramics

• (Nd1−xScx)2Zr2O7 ceramics were synthesized by solid state reaction.
• Pyrochlore phase in doped Nd2Zr2O7 had increased lattice parameter.
• Sc2O3 doping in Nd2Zr2O7 led to the formation of fluorite phase.
• (Nd0.9Sc0.1)2Zr2O7 exhibited the largest thermal expansion coefficient.

(Nd1−xScx)2Zr2O7 (x = 0, 0.1, 0.3, 0.5, 0.7) compounds were synthesized by solid state reaction at 1700 °C for 10 h, and characterized by XRD, Raman spectroscopy, SEM and high-temperature dilatometer. Nd2Zr2O7 exhibited pyrochlore phase, and its lattice parameter increased after Sc2O3 doping, which could be attributed to the presence of Sc3+ interstitial ions in pyrochlore lattice. Fluorite phase formed in the doped Nd2Zr2O7, and (Nd0.3Sc0.7)2Zr2O7 exhibited pure fluorite phase. The thermal expansion coefficient (TEC) of Nd2Zr2O7 was significantly enhanced by 10 mol% Sc2O3 doping, but higher Sc2O3 doping decreased the TEC. The reduced crystal energy due to the presence of Sc3+ interstitial ions could cause the initial increase in the TEC, and the formation of fluorite phase might contribute to the reduced TEC. Considering the alleviation of the thermal expansion mismatch stress for the high-temperature applications of Nd2Zr2O7, Sc2O3 was an excellent dopant and there existed an optimal Sc2O3 content for the optimization design of compound compositions.

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