Stabilization of cubic structure in Mn-doped hafnia

Abstract

The compounds Hf1−xMnxO 2−δ (x = 0 ∼ 0.5) have been synthesized by conventional solid state reaction method in Ar. Rietveld analysis of X-ray diffraction data has shown that the Mn-doped HfO2 undergoes a structural transformation from monoclinic to cubic phases, which is significantly dependent on the Mn content under current synthesis conditions. The stabilized cubic structure by multivalent Mn ion doping can transform to the monoclinic structure when annealed at high temperature in air. Transmission electron microscopy and electron diffraction investigations have also confirmed the existence of the high-temperature cubic structure. A mechanism of stabilizing the high-temperature cubic phase in the Hf1−xMnxO 2−δ system has been analyzed based on considerations of manganese substitution effect for hafnium ions and oxygen vacancy formation.

The Bright X‐Ray Stimulated Luminescence of HfO2 Nanocrystals Activated by Ti Ions

“…Indeed, the crystal phase transition from their monoclinic to the cubic arrangement can be achieved at low temperature by doping. In the literature, the origin of the stabilization of high‐temperature cubic phase in HfO 2 is related to both the dopant ion size and to the oxygen vacancies concentration, depending on the valence of the dopant substituting for Hf in the lattice . For instance, the stabilization of the cubic phase in these systems can be achieved through the incorporation of trivalent or divalent ions into the lattice, and the subsequent generation of oxygen vacancies for charge compensation .…”

A “green methodology” approach to the synthesis of HfO2 nanoparticles

“…Gao et al have reported the synthesis at 1400°C of micrometric particles of HfO 2 using a solid-state reaction [8]. HfO 2 nanoparticles in the size range of 25-75 nm were prepared by precipitation [9] and sol-gel [10] in the temperatures range of 500-800°C.…”

A nuclear hyperfine study of hafnium zirconate system

“…The study on the cubic HfO 2 -R 2 O 3 (R = Lu, Ho, Gd, Sm, Yb, Y and Sc) with R ?3 ions has revealed that the deep vacancy trapping leads to the decrease in the ionic conductivity at high dopant concentrations [6]. A recent study on the Mn-doped HfO 2 [5] reveals the fact that the Mn-dopant stabilizes the cubic phase of hafnia. The variable valences of Mn lead to the different ionic-sizes of Mn and the oxygen vacancies play an important role to stabilize the cubic phase.…”

“…At room temperature, ZrO 2 (baddeleyite) and isomorphous It has been observed that the property of the doped system gets modified significantly from its pure analogue in most of the cases [4]. There have been a number of studies on the stabilization of the high-temperature phases by doping with the suitable elements [5]. The doping with a tetravalent cation (same valence as of Hf 4?…”