Science Buddies: "Ask an Expert"

Hi

With this project, I am told that the physical properties of some crystals are different when measured in different directions in the crystal, and such a crystal is said to be anisotropic. Where resistivity is the physical property being investigated, how do I test to determine if a particular crystal is anisotropic (assuming that the small crystal is in the shape of a rectangular block, approximately 2mm in length)? Please, I would appreciate any help.

Thanks

Darien

You have picked a very challenging property to investigate. You need to do some research into conductivity/resistivity of irregular shaped objects. Even with materials that exhibit uniform directional conductance, the geometry of the contact area and the geometry of the material between the contacts will affect the overall conductivity/resistance between the contacts. You also have the problem of how you create the contacts. The contact to surface bond may not have a uniform resistance per area and it is extremely difficult to measure this.