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Measurement of the thermal diffusivity of thin films with bolometers and with pyroelectric temperature sensors

1991; Taylor & Francis; Volume: 118; Issue: 1 Linguagem: Inglês

10.1080/00150199108014776

1563-5112

B. Ploss, Siegfried Bauer, Cécile Bon,

Thermal properties of materials

Abstract Several methods for the measurement of the thermal diffusivity of thin films are developed. Common to all methods is the generation of a thermal wave via the absorption of intensity-modulated light on one surface of the film; resistive thin film bolometers and pyroelectric sensors are used for the temperature recording. For free-bearing films the thermal diffusivity is determined from front and rear side temperature spectra as a function of the modulation frequency, measured with resistive bolometers. If a pyroelectric material is mounted on a heat sink, the thermal diffusivity is obtained from the spectrum of the pyroelectric current. For very thin films pyroelectric substrates are recommended as temperature sensors. A novel method is also proposed, in which the thermal diffusivity is obtained without the influence of any other material properties and any sensor characteristics. Experimental results are presented with a 25 μm thick PVDF film and with a 1.25 μm thick Polyglutamate Langmuir-Blodgett film on a 9 μm thick PVDF substrate. The thermal diffusivity for the PVDF films is D = 6.2 × 10−8 m2/s and for the Polyglutamate Langmuir-Blodgett film D = 5.5 × 10−8 m2/s at room temperature. The techniques are theoretically discussed and various methods for the analysis of measured data are introduced.