Thermal properties of ZrB2-TiB2 solid solutions

Zirconium diboride ceramics were prepared with additions of up to 50 vol.% TiB2. The resulting (Zr,Ti)B-2 ceramics formed complete solid solutions based on x-ray diffraction. The addition of TiB2 resulted in grain size decreasing from 22 mu m for nominally pure ZrB2 to 7 mu m for ZrB2-50 vol.% TiB2. The thermal conductivity at 25 degrees C ranged from 93 W/m.K for nominally pure ZrB2 to 58 W/m.K for ZrB2-50 vol.% TiB2. Thermal conductivity was as high as 67 W/m.K for nominally pure ZrB2 at 2000 degrees C, but dropped to 59 W/m K with the addition of 50 vol.% TiB2. Electrical resistivity measurements were used to calculate the electron contribution to thermal conductivity, which was 76 W/m.K for nominally pure ZrB2 decreasing to 57 W/m.K when 50 vol.% TiB2 was added. The phonon contribution to thermal conductivity did not change significantly for <= 10 vol.% TiB2. Additions of >= 25 vol.% TiB2 reduced the phonon contribution to nearly zero for all temperatures.

Automated summary

Zirconium diboride ceramics were prepared with additions of up to 50 vol.% TiB2 and formed solid solutions. The addition of TiB2 resulted in decreased grain size and thermal conductivity. At high temperatures, the electron contribution to thermal conductivity was influenced by the addition of TiB2.