Laser Flash Technique (LFA)

Principle of the LFA Method

The laser or light flash method dates back to studies by Parker et al. in 1961. 

In carrying out a measurement, the lower surface of a plane parallel sample (see fig. 1) is first heated by a short energy pulse. The resulting temperature change on the upper surface of the sample is then measured with an infrared detector. The typical course of the signals is presented in figure 2 (red curve). The higher the sample’s thermal diffusivity, the steeper the signal increase.

a: Thermal diffusivity
ρ: Density
cp: Specific heat capacity
λ: Thermal conductivity
T:  Temperature
 

Using the half time (t1/2, time value at half signal height) and sample thickness (d), the thermal diffusivity (a) and finally the thermal conductivity (λ) can be calculated by means of the formula in figure 2. Furthermore, the specific heat (cp) of solids can be determined using the signal height (ΔTmax) compared to the signal height of a reference material. 

LFA investigations generally take much less time than thermal conductivity measurements by means of GHP (Guarded Hot Plate) or HFM (Heat Flow Meter).

 

Figure 1
Figure 2

NETZSCH LFA Systems

LFA 467 HyperFlash® – Light Flash Apparatus

The new LFA 467 HyperFlash® features a wide temperature range, very high efficiency (with its sample changer for 16 samples), extremely fast data acquisition rates and an intelligent lens system (ZoomOptics) between the sample and detector.

LFA 467 HT HyperFlash® – Light Flash Apparatus

The LFA 467 HT HyperFlash® allows for accurate thermal diffusivity and thermal conductivity measurements between RT and 1250°C with the smallest footprint on the market. The Ultra-fast sampling rate and extremely short pulse widths enable measurements of thin and highly conductive materials.

LFA 427 - Laser Flash Apparatus / Pyrometer version for up to 2800°C

Outstanding attributes of the LFA 427 are high precision and reproducibility, short measuring times, variable sample holders and precisely adjustable atmosphere conditions in the application range from -120°C to 2800°C. The LFA 427 is the most powerful LFA system for use in research & development.

LFA 457 MicroFlash® - Laser Flash Apparatus

The LFA 457 MicroFlash® is the most modern product for the determination of the two thermophysical properties, thermal diffusivity and conductivity, in the range from -125°C to 1100°C. Its compact, vacuum-tight construction, automatic sample changer and functional software guarantee the highest effectiveness for challenging materials testing.