Thermoelectric materials (TEs), which produce a voltage in response to an applied temperature gradient, are set to play an increasingly important role in the development of new energy efficient technologies by generating electrical current from waste heat. A performance gap exists between p-type and n-type oxide TEs, which presents a severe limiting factor on the application of oxide-based devices. We are attempting to develop new n-type oxide TEs with competitive ZT values by introducing complex structural ordering to suppress the lattice contribution to thermal conductivity, and by using chemical substitution to increase electrical conductivity, in four oxide solid solutions. We use neutrons to obtain accurate positions for oxide ions within the structures, and require high resolution data to solve the new crystal structures we have produced, and thus to understand their properties.