Dense K-beta -alumina ceramics were prepared by hot-pressing and hot-isostatic pressing (HIP) of calcined powders based on different alumina precursors. Maximum ionic conductivity as measured by AC-impedance spectroscopy was achieved in HIP'ed K-beta- and K-beta " -Al2O3 exhibiting a duplex microstructure. The synthesis of these microstructures can be targeted by the combination of more than one type of alumina precursor to introduce structural porosity at different times during the sintering process. This method reconciles the excellent beta -alumina phase formation capability of transition aluminas with their poor sintering quality.