Flux growth and state analysis of ilmenite and pyrophanite.

Abstract

Ilmenite and pyrophanite crystals were grown by the isothermal evaporations of an Na2B4O7 flux melt under various oxygen fugacities controlled by the mixed gas of CO2 and H2. Most crystals obtained were tabular with well-developed {0001} faces. Ilmenite crystals grown under higher fO2 conditions contain Fe3+ ions in several percents, and have smaller cell dimensions than those grown under lower fO2 conditions. Colors of pyrophanite crystals also seem to be affected by fO2 conditions, and cell constants decrease with increasing fO2' indicating that Mn3+ ions exist in pyrophanite grown under higher fO2 conditions. Intensity ratio (Lβ/Lα) of the Fe L (or Mn L) X-ray emission line slightly decreases for ilmenite (or pyrophanite) crystals grown under higher fO2 conditions, which seems to be consistent with the suggested existence of Fe3+ (or Mn3+) in ilmenite (or pyrophanite) crystals.