Grain-growth kinetics in wadsleyite: Effects of chemical environment

Grain-growth kinetics in wadsleyite was investigated using a multianvil high-pressure apparatus. Fine-grained wadsleyite aggregates were synthesized by isostatic hot-pressing and were subsequently annealed under high pressure and temperature in a controlled chemical environment. Wadsleyite samples show normal grain-growth characterized by a log-normal grain-size distribution following the relation, where n is a constant, L the grain-size at time t, L₀ the grain-size at time t = 0 and k is a rate constant that depends on temperature T and chemical environments (fO₂: oxygen fugacity in Pa, C_OH: water content in H/10⁶Si) as: