Dielectric Properties of Pure and Gd‐Doped HfO₂ Ceramics

Abstract

The pure, 2 at.%, and 20 at.% Gd‐doped HfO2 ceramics were prepared by the standard solid‐state reaction technique. Dielectric properties of these ceramics were investigated in the temperature range 300–1050 K and frequency range 20–5 × 106 Hz. Our results revealed an intrinsic dielectric constant around 20 in the temperature below 450 K for all tested ceramics. Two oxygen‐vacancy‐related relaxations R1 and R2 were observed at temperatures higher than 450 K, which were identified to be a dipolar relaxation due to grain response and a Maxwell–Wagner relaxation due to grain‐boundary response, respectively. The dielectric properties of the pure and slightly doped (2 at.%,) samples are dominated by the grain‐boundary response, which results in a colossal dielectric behavior similar to that found in CaCu3Ti4O12. The doping level of 20 at.% leads to the structural transformation from monoclinic phase to cubic phase. The dielectric properties of the heavily doped HfO2 are dominated by the grain response without any colossal dielectric behavior.

Phase stability, microstructure, and dielectric properties of quaternary oxides In12Ti10A2BO42 (A: Ga or Al; B: Mg or Zn)

“…Note in Table that all compounds present very good loss tangent behavior from RT up to ~673 K. In particular, ITAM and ITGM compounds show values as low as 0.0066 and 0.0042 at 473 K. Note also that the dielectric loss values are below 1 between 473 and 675 K. It is well known that a good dielectric material should have a very low dielectric loss (<1). The dielectric constant values measured in these materials are similar to those obtained in binary oxides with high dielectric constant, such as ZrO 2 (κ = 25, Tan δ = 0.02), HfO 2 (κ = 25‐40, Tan δ = 0.025) and La 2 O 3 (κ = 30), which are prominent candidates for integrated circuit devices (CMOS‐FET) . Robertson et al showed that the value of a dielectric constant tends to vary inversely with the band gap.…”

Structure and microwave dielectric characteristics of Hf1‐xTixO2 ceramics

“…Recently, Wang et al reported the dielectric properties of pure and Gd-doped HfO 2 ceramics. 12 On the other hand, the HfO 2 -TiO 2 system has attracted a lot of interest, [13][14][15] owing to its extremely low thermal expansion coefficient. Tilloca reported that HfO 2 -TiO 2 ceramics had been proven to have ultralow expansion and refractory properties.…”

“…Recently, Wang et al. reported the dielectric properties of pure and Gd‐doped HfO 2 ceramics 12 . On the other hand, the HfO 2 –TiO 2 system has attracted a lot of interest, 13–15 owing to its extremely low thermal expansion coefficient.…”

Effect of HfO 2 addition as intergranular grains on the energy storage behavior of Ca 0.6 Sr 0.4 TiO 3 ceramics

“…The intrinsic relative permittivity of HfO 2 was reported to be 18 [19], which is much smaller than CST (240). However, the addition of HfO 2 has limited effect on the dielectric properties of CST, probably due to its small concentration and special existence type as intergranular grains.…”