Hobbies And Interests
Piezoelectricity
Crystals become electrically charged when subjected to rotational forces by compression or twisting. This is the piezoelectric effect that also works in reverse. An electric charge applied to a crystal causes the crystal to vibrate. The frequency of the vibration depends on the way the quartz crystal is cut. Quartz crystals make accurate timepieces when cut to a consistent size and shape.
Pyroelectricity
Pyroelectricity is the property of materials to generate an electrical voltage when heated or cooled. Rotational forces are produced within the crystal lattice as it expands or contracts. Crystals of the compound lithium tantalite can be designed to emit electromagnetic radiation within a given wavelength. An array of crystals running on a laptop battery can be designed to produce X-rays for medical application.
Marangoni Convection
The production of crystals for industrial applications is achieved by growing the crystal slowly from a solution. The solution could be a solvent containing a compound or it could be molten metal. The aim is to produce a well-ordered structure that is free of contaminants. Surface tension at the interface between the solution and the atmosphere combines with the temperature gradient in the solution to create convection, a rotational force called Marangoni convection. Maragoni convection rotates through the solution and introduces defects into the crystal growth.
Czochralski Process
The Czorchralski process is an industrial technique to grow single crystals of semiconductors for electronic applications. It was pioneered in 1918 by Polish chemist Jan Czochralski. High purity silicon, or other metal as required, is melted in a quartz crucible. The process starts by dipping a rod with a seed crystal of silicon mounted on its tip into the melt. The seed crystal begins the process of crystal growth. The crystal is pulled upwards with the rod as it grows. The rod rotates during the pulling procedure producing a cylindrically shaped crystal. The Marangoni convection effects and potential defects in the crystal can be minimized or eliminated by rotating the crucible at the same time as the rod moves upwards. The three sets of rotational forces neutralize each other within the crystal.