Thermal Conductivity and Heat Capacity of α- and β-BaB2O4 Single Crystals

The thermal conductivity of beta- and alpha-BaB2O4 single crystals has been measured at temperatures from 50 to 300 K by a steady-state axial flow technique. The 300-K thermal conductivity of the beta-polymorph along and across its c axis is 1.64 +/- 0.08 and 1.24 +/- 0.06 W/(m K), respectively, and that of the alpha-polymorph along its c axis is 1.65 +/- 0.08 W/(m K). Swirls and twin boundaries have an insignificant effect on the thermal conductivity of alpha-BaB2O4 crystals. The heat capacity of alpha-BaB2O4 measured in the range 56-300 K using adiabatic calorimetry differs little from that of the beta-polymorph.