Yttria-stabilized zirconia is known to not be completely stabilized in the pure cubic YSZ phase up to temperatures above 1000 °C (Ref. and publications therein), commonly used abbreviations in conjunction with yttria-stabilized zirconia are: The thermal expansion coefficients depends on the modification of zirconia as follows: By the addition of yttria to pure zirconia (e.g., fully stabilized YSZ) Y ions replace Zr on the cationic sublattice. Thereby, oxygen vacancies are generated due to charge neutrality: formula_4 with formula_5, meaning two Y ions generate one vacancy on the anionic sublattice. This facilitates moderate conductivity of yttrium stabilized zirconia for O ions (and thus
Zirconium alloy zirconium alloys elevates requirement for their resistance to oxidation-related nodular corrosion. Furthermore, oxidative reaction of zirconium with water releases hydrogen gas, which partly diffuses into the alloy and forms zirconium hydrides. The hydrides are less dense and are weaker mechanically than the alloy; their formation results in blistering and cracking of the cladding – a phenomenon known as hydrogen embrittlement. Commercial non-nuclear grade zirconium typically contains 1–5% of hafnium, whose neutron absorption cross-section is 600x that of zirconium. Hafnium must therefore be almost entirely removed (reduced to < 0.02% of the alloy) for reactor applications. Nuclear-grade zirconium alloys contain more