Determining the Thermal Conductivity of Gehlenite by Thermal Microscopy at Room Temperature

The thermal conductivity of a single-phase gehlenite (2CaO Al 2 O 3 SiO 2 ) sample was determined using thermal microscopy. The composition of the primary crystal region of the gehlenite sample was CaO: SiO 2 :Al 2 O 3 = 38:28:34 (mass%), which was maintained after melting and cooling. After polishing the samples, the size of the gehlenite crystal was sufficiently large to be measured using a thermal microscope. The value of λ C ρ , where λ is thermal conductivity C is specific heat andρis density, of the samples was measured every 10 μm to obtain its distribution. When comparing the results with the optical microscopy image of the sample, the gehlenite region showed a larger value of λ C ρ than the glassy region. Specifically, the value of λ C ρ of the gehlenite region was determined to be 2.2 ± 0.1 kJs −0.5 ·m −2 ·K −1 , which resulted in a thermal conductivity of 2.1 ± 0.2 Wm −1 ·K −1 . Moreover, the oxide gehlenite phase showed lower thermal conductivity than the other constituent phases, i.e., CaO, Al 2 O 3 , and SiO 2 .