In the new class of iron pnictide superconductors, there is evidence of phase coexistence close to the phase boundary between the SDW and superconducting order produced by hole or electron doping. NMR experiments on both BaFe2-xCoxAs2 and Ba1-xKxFe2As2 samples have indicated that the nature of the phase competition is quite different. In the former, there is a coexistence of SDW and superconducting order on a microscopic length scale, whereas, in the latter, the two phases are mesoscopically phase segregated. We have recently optimized the synthesis conditions for producing more homogeneously K-doped samples, and shown that the superconducting transition at x=0.2 is much lower than previously reported and there is no SDW order at high temperature, in contradiction with the existing literature. We therefore propose to investigate the phase diagram of Ba1-xKxFe2As2 in more detail.