The BIMR houses one of the most extensive collections of crystal growth infrastructure in North America. These growth facilities include:
- 3 Floating Zone Optical Image Furnaces
- DC tri-ARC Crystal Growth Station
- Skull-Melt Station
- Computer-assisted Czochralski Furnace
- Directional Solidification/Bridgman Furnaces
- Flux Growth Laboratory
- Crystal cutting and polishing equipment
This suite of infrastructure enables the growth of single crystals of virtually all classes of inorganic materials. They enable growth of materials that 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.
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.
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.
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.