The thermal conductivity of alumina varies with temperature, and what can be added to the raw material composition to increase the thermal conductivity

Aluminum oxide, as an important inorganic non-metallic material, has a wide range of applications in fields such as electronic packaging and thermal management materials. Its thermal conductivity is one of the key factors affecting material properties and application effects.

The variation of thermal conductivity of alumina with temperature
The thermal conductivity of alumina is closely related to temperature. At very low temperatures, the contribution of the heat capacity Cv to the thermal conductivity λ varies with Cv and T3. As the temperature increases, the thermal conductivity rapidly increases. However, as the temperature continues to rise, the average free path decreases, and the rate of increase in thermal conductivity with increasing temperature slows down, approaching a certain value around the Debye temperature θ d. Afterwards, the mean free path became the main factor affecting thermal conductivity, leading to a rapid decrease in thermal conductivity with increasing temperature. At low temperatures (such as 40K), the thermal conductivity reaches a maximum value; In high temperature regions (such as 1600K), the thermal conductivity increases due to the contribution of photon thermal conductivity.

The influence of raw material composition on the thermal conductivity of alumina
To improve the thermal conductivity of alumina, specific raw material components can be added.
Here are some effective methods:
Add thermal conductive agent:
Copper oxide: Copper oxide is a commonly used thermal conductive agent with higher thermal conductivity than aluminum oxide. By uniformly mixing copper oxide and aluminum oxide, a thermally conductive composite material can be formed, thereby improving the thermal conductivity of aluminum oxide.
Silicon dioxide and silicon nitride: These materials can also be added as thermal conductivity agents to aluminum oxide to improve its thermal conductivity.
Control granularity size:
Particle size is one of the key factors affecting the thermal conductivity of alumina. Generally speaking, the smaller the particle size, the higher the thermal conductivity of alumina. Therefore, aluminum oxide can be processed by mechanical ball milling, ultrasonic dispersion and other methods to obtain smaller particle sizes, thereby improving its thermal conductivity.
Mixing and filling with different particle sizes:
By mixing and filling alumina particles of different sizes, a more compact packing structure can be formed, increasing the filling amount and creating a good thermal conductivity pathway. This method helps to improve the thermal conductivity of composite materials.
Increase alpha phase content:
Alpha phase alumina has high stability and crystallinity, which helps to improve the thermal conductivity of the material. Therefore, when selecting alumina raw materials, priority should be given to products with high alpha phase content.
Surface modification:
The surface polarity of alumina is strong, and its compatibility with the organic resin matrix interface is poor. Surface modification treatment, such as coupling agent treatment, can improve the interfacial adhesion between alumina and polymer matrix, reduce agglomeration phenomenon, and thus enhance the thermal conductivity of composite materials.

Considerations in practical applications
In practical applications, in addition to considering the influence of raw material composition on the thermal conductivity of alumina, the following points should also be noted:
Polymer matrix types: Different polymer matrices have different effects on the compatibility and dispersibility of alumina thermal conductive powder. Therefore, when selecting a polymer matrix, it is necessary to fully consider its compatibility with alumina.
Alumina content: Although the higher the alumina content, the higher the thermal conductivity of the composite material, excessive content may lead to a decrease in other properties of the composite material, such as mechanical or electrical properties. Therefore, it is necessary to determine the appropriate alumina content based on specific application scenarios and requirements.
Processing conditions: Mixing and processing conditions such as stirring speed, temperature, and time can also affect the dispersion of alumina in the polymer and the performance of the final composite material. Therefore, strict control of processing conditions is required during the preparation process.

The thermal conductivity of alumina shows a certain pattern with temperature changes, and its thermal conductivity can be improved by adding specific raw material components. In practical applications, it is necessary to comprehensively consider factors such as raw material composition, polymer matrix type, alumina content, and processing conditions to prepare high-performance alumina thermal conductive materials.