What is the flux method?

The flux method is the world's leading manufacturing process for growing inorganic single crystals, which is led by Shinshu University.

In order to obtain high-quality crystals, it is necessary to dismember the atoms of the material (liquid or gas) and rearrange them in an orderly fashion. In general, crystal growth is performed by heating the material to the melting point of the material to produce a melt, which is then cooled and crystallized.

In the flux method, the solute (raw powder) is heated and melted into the flux material and crystals are grown by utilizing  the increase of supersaturation due to cooling and flux evaporation.

For example, when converting salt into a liquid, it must be heated to a temperature where the solid is converted to a liquid (about 800°C, the melting point), but if it is dissolved in water, it can be converted to a liquid at room temperature. Thus, the flux method is a technology for producing high-quality crystals at temperatures far lower than the melting point by using a solvent (flux).

Image of crystal growth using the flux method

Typical Characteristics of the Flux Method

High quality single crystals can be grown.

High quality single crystals with the features of low thermal distortion, self-shape (original crystal shape) and uniform grain size can be grown.

Crystal form (crystal face) can be controlled.

By changing the conditions of crystal growth (raw materials, atmosphere, type of solvent, temperature, holding time, cooling conditions, etc.), crystal morphology (crystal face) can be controlled and high functionality can be easily materialized.

Simple equipment and easy operation (low cost)

Energy source (e.g., a) If you have a recipe (electric furnace) and a recipe (crystal growth conditions), you can create crystals.

Growth of crystals at a temperature lower than the melting point (approx. 100℃ or higher) *Depends on the target crystals

Crystal growth time varies from several tens of minutes to several tens of hours depending on the target crystal.

Features of Shinshu University Flux Technology

  • The Teshima-Zettsu  Laboratory at Shinshu University is a one and only research center for flux science, and possesses one-of-a-kind crystal growth technology.

  • We hold  more than 300 different crystal growth recipes that we have accumulated over 50 years.

  • Generally, university produce materials on a small scale (gram-order), but at Shinshu University, some materials can be produced on a semi- production level (hundreds of gram or kilogram order).

Examples of various crystals grown by flux technology

What is the flux coating method?

This is a coating technology based on the principles of the flux method.

A crystalline layer (thin film) can be created on the surface of various base substarate materials by applying a paste (solution) sample to the base material and crystallizing it.

Characteristics of the flux coating method

Simple equipment and processes

High quality crystal layers can be formed.

High quality and morphology control, which are the characteristics of  crystals made by flux method , are preserved.

Direct growth from the substrate surface

Application example: Apatite crystal growth by flux coating method

Hydroxyapatite coating on Ti substrate

Coating on various substrates

Fluorine apatite coating

Apatite is a material that constitutes bones and teeth, and is used as a biomaterial for various applications due to its high biocompatibility.

Application example: Adding functions by flux coating

in preparation

Application example: growing thin and thick films by flux coating

Al2O3:Cr (Ruby)