Non stoichiometry and lattice expansion of BaZr0.9Dy0.1O3-δ in oxidizing atmospheres

Why is it so difficult to realize Dy$^{4+}$ in as-synthesized BaZrO$_3$?

“…We examine defect landscape in BaZrO 3 in two limits: (i) the (Ba,O)-rich condition where the host material is assumed to be in thermodynamic equilibrium with BaO (∆H = −5.09 eV) and O 2 gas at 1 atm, and (ii) the (Zr,O)-rich condition where equilibrium with ZrO 2 (∆H = −10.99 eV) and O 2 gas at 1 atm is assumed. The temperature range from 1000 • C to 1600 • C is often used in the preparation of Dy-doped BaZrO 3 samples [4][5][6]8]. Under the mentioned conditions, µ O is −1.45 eV (at 1000 • C) or −2.56 eV (1600 • C) [18].…”

“…Dysprosium (Dy) is very stable as the trivalent Dy 3+ in solid compounds, yet the divalent Dy 2+ has also been observed in some fluorides [1,2] and suspected to be photogenerated under irradation in persistent luminescent phosphors [3]. The tetravalent Dy 4+ was unknown up to very recently [4][5][6]. Han et al [4] was the first to claim experimental evidence of Dy 4+ in BaZrO 3 , a perovskite structure type host lattice commonly investigated for its proton conductivity ability [7].…”

“…Han et al [4] was the first to claim experimental evidence of Dy 4+ in BaZrO 3 , a perovskite structure type host lattice commonly investigated for its proton conductivity ability [7]. Subsequent experimental reports provided further evidence for the presence of the tetravalent state in samples prepared in oxidizing atmospheres [5,6] and the mixed-site occupancy of Dy in the host lattice [8], and discussed the possible role of Dy 4+ as a charge-compensating defect in the oxidation reaction [5,6]. The stability of Dy 4+ is thus of interest because of not just the exotic tetravalent state but also the implication it has for defect-related processes in the material.…”

Modeling Electro-Chemo-Mechanical Behaviors within the Dense BaZr0.8Y0.2O3−δ Protonic-Ceramic Membrane in a Long Tubular Electrochemical Cell

“…5 × 10 −6 m 3 mol −1 . Ricote et al [24] showed that the O-site polarons produce negligible chemical expansion. The present model attributes all chemical expansion to the protons, neglecting lattice distortion due to polarons and oxygen vacancies.…”

“…Dubois et al [23] developed a coupled chemo-thermo-mechanical model using an extended Nernst-Planck formulation and evaluated the stresses associated with a protonic-ceramic fuel cell (PCFC) in a button-cell configuration. Ricote et al [24] used high-temperature X-ray diffraction (HT-XRD) and thermogravimetric analysis (TGA) to study the effects of oxygen partial pressure on lattice parameters and oxygen nonstoichiometry in BaZr 0.9 Dy 0.1 O 3−δ (BZDy10).…”