Effect of high-content Yttria on the thermal expansion behaviour and ionic conductivity of a stabilised cubic Hafnia

Stability of doped zirconia under extreme conditions: Toward long‐term and secure storage of radioactive waste

“…This behavior is explained by higher yttrium content which, in turn, yields a higher bulk modulus with resulting decrease in CLTEs of YSZ. 17 Similar reduction in thermal expansion coefficients was observed in related Y-doped HfO 2 phases 18 upon the introduction of trivalent yttrium atoms and was shown to be related to increase in oxygen vacancies. On the contrary, doping with larger Ce 4+ ions induces minor but steady increase in CLTEs for both tetragonal and cubic Ce-YSZ phases (Table 1).…”

First Demonstration of Yttria‐Stabilized Hafnia‐Based Long‐Retention Solid‐State Electrolyte‐Gated Transistor for Human‐Like Neuromorphic Computing

“…Imaginary impedance has a negative value because the metal-electrolyte-metal structure can be represented by a parallel circuit of a capacitor and resistor. [14,[20][21][22] In EIS analysis, the impedance converges to the resistance of the metal electrodes at very high frequencies, but both the real and imaginary parts of the impedance increase as the frequency decreases. When the frequency decreases more than the relaxation frequency, the imaginary part of the impedance starts to decrease and the real part increases, exhibiting a semicircular shape.…”

“…In addition, a lower ionic conductivity is exhibited for higher yttrium concentrations at all temperatures, following the Nernst-Einstein equation, which represents the ionic mobility when an electric field is applied to the electrolyte. [14,24] The decrease in ionic conductivity with an increase in the yttrium concentration in the YSH film can be explained by the crystal structure of the cubic YSH and the association between the yttrium cations and oxygen vacancies. [14,25] The transition of the most stable crystal structure and bonding when yttrium is doped in HfO 2 is shown in Figure 2d.…”

“…[14,24] The decrease in ionic conductivity with an increase in the yttrium concentration in the YSH film can be explained by the crystal structure of the cubic YSH and the association between the yttrium cations and oxygen vacancies. [14,25] The transition of the most stable crystal structure and bonding when yttrium is doped in HfO 2 is shown in Figure 2d. The crystallographic structure of YSH and HfO 2 in Figure 3d is obtained with first-principles simulation using Generalized Gradient Approximation (GGA) with Perdew-Burke-Ernzerhof (PBE) functional to conduct Discrete Fourier Transform (DFT) analysis.…”

“…[3][4][5] In particular, the electrolyte characteristics of yttria-stabilized hafnia (YSH) have been reported recently. [14,15] In the solid-state electrolyte YSH, it has been found that the ionic conductivity inside the electrolyte can be controlled according to the yttrium doping concentration; however, a device using YSH has not yet been developed.…”