Rare earth zirconates have been considered as promising candidates for thermal barrier coatings, with extremely low thermal conductivity which is usually attributed to their unique pyrochlore/fluorite structure. In order to investigate the different influence of pyrochlore and fluorite structure on thermal conductivity, Gd2Zr2O7 ceramics with pyrochlore and fluorite structure were prepared separately by controlling the sintering temperature, and the thermal conductivities of the samples sintered at different temperatures were measured and investigated. The results show that the structure of Gd2Zr2O7 changes gradually from pyrochlore to fluorite as the sintering temperature increases from 1450°C to 1600°C, accompanying with a thermal conductivity decreasing first and then increasing. The minimum value of thermal conductivity appears on the sample with pyrochlore structure nearby the phase transition temperature range, rather than that with fluorite structure. Other than the transition of structure, structural distortion in the lattice approaching phase transition may lead to a distinct decrease of thermal conductivity.
In this paper, a series of non-stoichiometric Sm2+xZr2-xO7-x/2 (x=0, 0.2, 0.4, 0.6) were synthesized by chemical co-precipitation method. He2+ ion irradiation experiments were carried out with irradiation energy of 500 KeV and irradiation flux of 5×1016 ions/cm2. Effect of He2+ ion irradiation on the crystal structure was characterized by XRD, GIXRD, and Raman spectroscopy. The XRD patterns show that all the peaks shift to lower diffraction angles and the characteristic peaks of pyrochlore structure weaken after irradiation, which suggests an expansion of the lattice and the degeneration of pyrochlore structure. Moreover, the GIXRD patterns reveal the existence of an irradiated layer on the surface of the sample.
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