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Centre for Crystal Growth (CCG)

The BIMR houses one of the most extensive sets of crystal growth infrastructure in North America. These growth facilities include:

  1. 2 Floating Zone Optical Image Furnaces
  2. DC tri-ARC Crystal Growth Station
  3. Skull-Melt Station
  4. Computer-assisted Czochralski Furnace
  5. Directional Solidification/Bridgeman Furnaces
  6. Flux Growth Laboratory

This suite of infrastructure enables the growth of single crystals of virtually all classes of inorganic materials. They enable growth of materials which melt congruently, and those that do not, and therefore require a flux. The most recent addition to this suite of crystal growth apparatus is the two floating zone optical image furnaces, which are optimized for large single crystal growth of oxide materials. This $1M image furnace laboratory is one of only two such facilities in Canada, and is the most advanced of its kind in Canada. Single crystals of new magnetic and superconducting oxides weighing as much as 10 grams have been grown in this laboratory. The resulting single crystals are in pristine form, as no crucible is used in image furnace growth.

In addition to single crystals grown for Brockhouse Institute members, crystals have been grown for Birgeneau (Toronto), Taylor (Queen's), Tranquada and Gu (Brookhaven), Schlom (Penn State), Imanaka (Osaka), and Bjork (Upsala). The ability of the Institute to provide state-of-the-art crystals frequently serves as a gateway for Institute faculty to participate in important international collaborations.

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A single crystal grown from solution.  The growth of large and pristine single crystals of new materials is central to our research program. Our research projects really begin with materials preparation and crystal growth, and only if that is successful do we undertake the scattering studies. I prefer to have all of my graduate students have experience with crystal growth, as it is an important and under-appreciated technical competence which will serve them well in their future careers.

We produce most of the single and polycrystalline materials that we study with scattering techniques. We sometimes are given crystals by other crystal growers (for example, we’ve had a very successful collaboration with Prof. F. C. Chou of the National Taiwan University on unconventional spin-Peierls systems TiOBr and TiOCl), but mostly we make our own materials. This allows us to set up long term and systematic studies of entire families of materials, and to explore certain themes in condensed matter physics.iOCl), but mostly we make our own materials.

The cornerstones of our crystal growth effort are two Floating Zone Image Furnaces. Polycrystalline starting material of the desired composition, or material close to the desired composition, is placed near one of the common focii in a 2 or 4 elliptical mirror cavity. Halogen light bulbs placed at the other elliptical mirror focii ensure that light is focused at the sample position, producing a “hot spot” which is only a few mm across. Depending on how well the material absorbs the light, the “hot spot” may be locally heated up to as high as 2200 C, which is enough to melt most materials. A molten zone is then formed at the common focus, and it is held in place by the surface tension of the molten material. Then, either the polycrystalline sample, or the mirror assembly, or both, can be translated such that the molten zone passes along the polycrystalline rod. The polycrystalline rods are placed in a sealed quartz tube, so that the crystal growth can be carried out in specialized oxidizing or reducing, or inert atmospheres – up to 10 atmospheres. If everything works well, a zone refined single crystal is left behind the passing molten zone, and a high quality single crystal of approximate dimensions 5mm diameter by 50 mm long is produced.

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One of our two Optical Floating Zone Furnaces (two mirror type), with a ceramic that has been melted at the "hot spot".

These furnaces are particularly well suited to growing large single crystals of transition metal oxides. Our recent successes have been the cubic pyrochlores Yb2Ti2O7, Er2Ti2O7, Tb2Ti2O7, Ho2Ti2O7 ; kagome staircase materials Co3V2O8; high temperature superconductors La(2-x)Ba(x)CuO4, Bi2Sr2CaCu2O8; and quantum magnets SrCu2(BO3)2 and CuGeO3.

A very important prerequisite for all single crystal growth is the capacity to make the polycrystalline materials which are the starting point. We have extensive facilities for the accurate weighing, mixing, and annealing of polycrystalline materials, as well as infrastructure, such as x-ray diffraction capabilities, which allow us to assess whether or not the starting polycrysyalline material is what we think it is.

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An example of a finished floating zone growth. The ceramic starting material (the "seed rod") is still attached to the single crystal growth.

We also perform some Flux Growth which involves slow cooling of a melt, and single crystals are then cut out of the resulting boule. We have the capacity for performing Growths from supersaturated solution, Bridgeman growths, Czochralski growths, as well as Tri-Arc growths for intermetallic materials.

Taken together, the infrastructure for both crystal growth and for the assessment of crystalline materials in the Centre for Crystal Growth is the most sophisticated and extensive of its type in Canada, and one of the most sophisticated in North America. This infrastructure underpins our entire program in the advanced characterization of materials with exotic ground states.