The incorporation of Gd into HfO2 thin films is shown to induce ferroelectricity. A significant influence of electric field cycling on both polarization as well as small-signal capacitance-voltage measurements can be observed. X-ray diffraction measurements are supported by infrared absorption analysis and give further evidence of the previously proposed non-centrosymmetric transition phase of space group Pbc2(1). (C) 2012 The Electrochemical Society. All rights reserved.