In experiments, powders of various compositions were synthesized by a modified sol-gel method and calcined at appropriate temperatures to convert them into compounds of pyrochlore structure as confirmed by x-ray diffraction. These powders were hot pressed into dense disks of 1-in. (2.54-cm) diameter. The thermal conductivities of the disks were measured at various temperatures up to 1,550 °C by use of a steady state laser heat-flux technique. The figure presents results of such measurements performed on several materials of general composition La2–x(Gd and/or Yb)xZr2O7, where x = 0 or 0.3. The thermal conductivities of all doped samples (x = 0.3) were less than those of the undoped (x = 0) sample [La2Zr2O7]. The lowest conductivity — ranging from 40 to 50 percent below that of undoped sample — was exhibited by the sample co-doped with both Gd and Yb.

This work was done by Narottam P. Bansal of Glenn Research Center and Dongming Zhu of the U. S. Army Research Laboratory. For further information, access the Technical Support Package (TSP) free on-line at under the Materials category.

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Refer to LEW-17469-1.