抄録
The spot heating method has been developed as a new method for measuring the thermal conductivity (λ) and the thermal diffusivity (κ) of thin materials.
The principle of this measurement is based on three relations between the temperature increase of the sample surface heated by the laser beam and the thermophysical properties of the sample. These relations are obtained by solving the Fourier’s equation under different ranges of time. The temperature increase measured in a short time range is proportional to the square root of time. The slope of this straight line gives the value of λ⁄κ1⁄2. On the other hand, the temperature increase of a long time range is inversely proportional to the square root of time. The slope of this line offers the value of λκ1⁄2 and the intercept at 1⁄t1⁄2=0 gives λ. Therefore, the thermal conductivity and the thermal diffusivity can be determined by using two of the above three relations.
With the use of this method, first, the thermal conductivity and the thermal diffusivity of thick materials with a thickness of about 10 mm have been measured at room temperature. Fused-SiO2, PbO-SiO2, glass plates, micas and silicone rubbers are employed. The results are in good agreement with the literature values.
Second, this method has been successfully applied to thin materials of 200 μm-1 mm in thicknesses, such as fused-SiO2 plates, glass plates and photoresist films without the influence of substrates. The obtained values are also in good agreement with the values of the thick materials.
Finally, errors and the potentiality of its application to thin films have been discussed in detail.
The spot heating method may be of great promise for the measurements of the thermal conductivity and thermal diffusivity of various materials, especially thin materials.
