3The physical and electrical properties of noncrystalline Hf-alumiunate alloys, (HfO2)(x)(Al2O3)(1-x), were investigated. Characterization by Auger electron spectroscopy and Fourier transformation infrared spectroscopy confirm these alloys are homogeneous and pseudobinary in character, displaying increased thermal stability against crystallization with respect to the respective end-member oxides. Capacitance-voltage and current density-voltage data as a function of temperature demonstrate that the Hf d states of these alloys act as localized electron traps, and are at an energy approximately equal to the conduction band offset energy of WO, with respect to Si. This work also provides additional insight into a previously reported study of Ta-aluminate alloys with localized electron traps associated with d states of the Ta atoms.