We seek high-resolution powder neutron diffraction data at room and low temperature to help in the identification of the structure of new Pb-free piezoelectric materials we have designed. We have used design principles developed from decades of study on Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) solid solutions, which have the best piezoelectric response of any material known. The best performing PMN-PT compositions have subtle monoclinic distortions, which required low temperature neutron data to definitively assign. We believe we have replicated this chemistry in a Pb-free system, but need to study the structure in detail to fully understand the similarities and differences between the Pb-based and Pb-free systems.