BiFeO3 is one of the most widely studied multiferroics (ferroelectric TC ~ 830°C, and antiferromagnetic TN ~ 370°C). Rare earth doping has been shown to be a suitable method of overcoming problems associate both with phase metastability and over-riding electrical conductivity which have hampered technological application of this material. We request beamtime to determine the structural phase diagrams of BiFeO3 doped with La and Nd. Specifically we aim to investigate: 1) the extent of the reported anitpolar Pbam phase in Nd-BiFeO3; 2) the possibility of successive polar R3c to antipolar Pbam to non-polar Pbnm transitions in Nd-BiFeO3; and 3) confirm our assignent of Imma for La-BiFeO3 and any subsequent transformation to Pbnm. The presence of such transformations are supported by dielectic data which will be used to target key temperature ranges for this structural study.