Measuring the Thermal Diffusivity

The rate at which a substance reacts to changes in temperature depends on its thermal conductivity, its density and its specific heat capacity. The thermal conductivity determines how quickly the heat spreads in a fabric. The specific heat capacity indicates how much of this heat is stored in the fabric. The density takes into account how much substance per cubic meter is present. These relationships are described by the thermal conductivity. This substance size is equal to the quotient of thermal conductivity and the product of specific heat capacity and density. From this formula, the unit of measure [m²/s] is calculated.

The thermal diffusivity is required for the assessment of heating and cooling processes, temperature changes in living spaces and thermal stresses in components. For example, the indicator is an important criterion in the classification of civil engineering equipment to prevent fire spread.

If a fast temperature compensation in materials is desired, materials with a high thermal conductivity are advantageous. These include metals and graphite. These substances are used for example in temperature measuring instruments and temperature controllers. Non-metals conduct the temperature significantly worse. They are suitable, among other things, for heat storage in regenerators.

For the measurement of the thermal diffusivity, a material sample is placed between two elements with constant, mutually different temperatures and the local and temporal temperature profile in the sample is evaluated. These elements can be found, for example, in the LINSEIS Heat Flow Meter. Precise measurement data for very thin layers is provided by our TF-LFA – LaserFlash for thin films, which works on the basis of laser beams. The Linseis gauges simultaneously determine the thermal conductivity, the thermal diffusivity and the specific heat capacity based on the included software.

Applications measuring thermal diffusivity

Application: Measuring Cermaic Filled Polymers using THB

Linseis application curve - Ceramic Filled Polymer - using THB

Application: Isotropic graphite (AIST) using LFA

Linseis application curve - Isotropic graphite (AIST) using LFA

This graph shows the Thermal Diffusivity values measured on a LINSEIS LFA 1000 compared to the values measured at AIST* Japan. The literature values of the used Isotropic Graphite from AIST* the measured results on the LFA 1000 vary by less than 2 %.

Our devices for thermal diffusivity

LFA 500


LFA 500 – LightFlash Analyzer – The robust workhorse


LFA 1000


LFA 1000 – True LaserFlash Analyzer – The premium device




Thin Film LaserFlash – Time Domain ThermoReflectance (TDTR)- Thermal diffusivity of thin films



Linseis THB

THB – Transient Hot Bridge – Sandwiched Sensor type Thermal Conductivity and Thermal Diffusivity measurements




Unique device for a comprehensive thin film characterization from the nm to the µm scale


LZT Meter


LZT-Meter – Perfect tool for thermoelectric applications



Linseis HFM

HFM – Heat Flow Meter – The perfect solution for isolating materials