Antiferroelectricity in ZrO2 and Ferroelectricity in Zr, Al, La Doped HfO2 Nanoparticles

The dependence of the polarization P in Hf1-xZrxO2 nanoparticles on electric field, dopant concentration x, size and temperature are studied using the transverse Ising model and the Green’s function method. Pure ZrO2 shows at high electric fields an antiferroelectric behavior. Pure HfO2 is a linear dielectric in the monoclinic phase. With increasing ZrO2 content the of HZO shows a ferroelectric behavior. The composition dependence x of the remanent polarization Pr(x) has a maximum for x = 0.5. For x = 0, pure HfO2, and x = 1, pure ZrO2, Pr=0. P increases with decreasing HZO nanoparticle size. The influence of Al and La doping on Pr in HfO2 nanoparticles is also studied. The exhibiting of the ferroelectricity in ion doped HfO2 is due to a phase transformation and to an internal strain effect. The observed results are in good qualitative agreement with the experimental data.