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

The thermal conductivity of a single-phase gehlenite (2CaO -Al2O3 -SiO2) sample was determined using thermal microscopy. The composition of the primary crystal region of the gehlenite sample was CaO: SiO2:Al2O3 = 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 root lambda C rho, where lambda is thermal conductivity C is specific heat and.is density, of the samples was measured every 10 mu m to obtain its distribution. When comparing the results with the optical microscopy image of the sample, the gehlenite region showed a larger value of root lambda C rho than the glassy region. Specifically, the value of root lambda C rho of the gehlenite region was determined to be 2.2 +/- 0.1 kJs(-0.5)center dot m(-2)center dot K-1, which resulted in a thermal conductivity of 2.1 +/- 0.2 -Wm(-1)center dot K-1. Moreover, the oxide gehlenite phase showed lower thermal conductivity than the other constituent phases, i.e., CaO, -Al2O3, and -SiO2.