Growth and characterization of synthetic iron-bearing olivine

Single crystals of olivine were grown at 0.1 MPa total pressure in a floating-zone image furnace. Composition of crystals grown ranged from 67 mol% forsterite to 90 mol% forsterite. Improvements in the crystal growth technique allowed growth of large crystals (0.005 m diameter, 0.070 m length) with very low dislocation density, no visible bubbles, and no cracks. The most significant improvement was the addition of a platinum-wound resistance heater internal to the image furnace. This heater provided the dual improvements of better control over oxygen fugacity from a CO/CO₂ gas mix and alteration of the crystal growth interface resulting in a significant reduction in crystal defects. No subgrain boundaries have been observed in crystals growth here and dislocation densities on the order of 10⁸-10⁹ m^-2 have been achieved. Iron concentration is nearly uniform across the diameter (0.005 m) of crystals and varies approximately 5 mol% along the crystal length (0.040 to 0.050 m).