Glycol-citrate synthesis of fine-grained oxides La2−xGdxZr2O7 and preparation of corresponding ceramics using FAST/SPS process

Single-phase superfine refractory oxides of composition La2−xGdxZr2O7 (x = 0, 0.5, 1, 1.5, 2) have been synthesized using glycol-citrate route. Dependencies of degree of dispersion and phase composition on chemical composition for such oxides were determined. Fluorite-pyrochlore transition observed during thermal treatment of these oxides was examined. It was stated that this transition occurred in the temperature range 1000-1200 °C for all formulations with exception of gadolinium zirconate Gd2Zr2O7 which kept the fluorite structure even after long-term exposure (4 h) at a temperature of 1400 °С. Samples of corresponding ceramics which density amount to 95-98% of the theoretical value were obtained using FAST/SPS process. Coefficients of linear thermal expansion (CLTE) of manufactured materials were measured. It was found that CLTE values for all samples except for gadolinium zirconate were independent of temperature in the range 400-1000 °C. It was shown that Gd2Zr2O7 kept the fluorite structure under conditions of FAST/SPS process at a temperature of 1600 °C.