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

A. T. Apostolov, I. N. Apostolova, J. M. Wesselinowa
2020 Advances in Materials Physics and Chemistry  
The dependence of the polarization P in Hf 1-x Zr x O 2 nanoparticles on electric field, dopant concentration x, size and temperature are studied using the transverse Ising model and the Green's function method. Pure ZrO 2 shows at high electric fields an antiferroelectric behavior. Pure HfO 2 is a linear dielectric in the monoclinic phase. With increasing ZrO 2 content the ( ) P E of HZO shows a ferroelectric behavior. The composition dependence x of the remanent polarization ( ) r P x has a
more » ... n ( ) r P x has a maximum for x = 0.5. For x = 0, pure HfO 2 , and x = 1, pure ZrO 2 , 0 r P = . P increases with decreasing HZO nanoparticle size. The influence of Al and La doping on r P in HfO 2 nanoparticles is also studied. The exhibiting of the ferroelectricity in ion doped HfO 2 is due to a phase transformation and to an internal strain effect. The observed results are in good qualitative agreement with the experimental data. − − − ( ) ij i j J J r r = − in the defect sizes (denoted as d J ) compared to the undoped samples. The radius of the tetravalent Zr ion (86 pm) is a little larger than that of the Hf ion (85 pm), i.e. there is a small tensile strain ( d b J J < ), in agreement with the experimental data A. T. Apostolov et al. d J = ); (2) La ( 451 K d J = ) ions. A similar behavior for the Al concentration dependence of the dielectric constant in HfO 2 thin films is reported by Yoo et al. [43]. The electric properties of La doped HfO 2 NPs are also studied. The radius of the La ion (117.2 pm) is larger compared to the ionic radius of Hf (85 pm) (this means d b J J < ). Batra et al. [31] have shown that La doping stabilizes the or-A. T. Apostolov et al.
doi:10.4236/ampc.2020.102003 fatcat:tu4hatqxxrhgrgxh6brovy5w7e