Yttria-stabilized zirconia

Yttria-stabilized zirconia (CAS 64417-98-7), commonly abbreviated YSZ, is a zirconia ceramic in which yttrium oxide (Y₂O₃) is incorporated into the ZrO₂ lattice at concentrations typically ranging from 3 to 8 mol % to stabilize the tetragonal or cubic phase and suppress the detrimental monoclinic transformation on thermal cycling. Related identifiers include the alternative CAS 114168-16-0, used for certain 8YSZ and thermal-spray grades, while designations such as Y-TZP (3 mol %), 8YSZ, PSZ, and 7YSZ refer to compositional variants of this same product family.

Where is Yttria-stabilized zirconia used?

• Aerospace and defence: 7YSZ thermal-spray powder for thermal barrier coatings (TBCs) on gas turbine hot-section components, requiring low thermal conductivity and phase stability up to approximately 1,200 °C
• Energy: 8YSZ electrolyte layer in planar SOFC and SOEC stacks; active ceramic in lambda (λ) and oxygen sensor elements for automotive exhaust aftertreatment and industrial process-gas monitoring
• Automotive and building & construction: Y-TZP precision wear parts, pump components, cutting tools; spray-dried 3Y-TZP granules for dry-pressing and cold isostatic pressing (CIP) of shaped parts
• Grinding media in bead form (0.5–2.0 mm diameter, bulk density approximately 3.7 kg/L, specific gravity approximately 6.1 g/cm³, Vickers hardness HV1 ≥ 1,250) are widely used for fine milling of electronic and piezoelectric ceramics.

Good to know: The 3 mol % grade (approximately 5.2 ± 0.5 wt % Y₂O₃, Y-TZP) delivers the highest mechanical strength and transformation-toughening response, making it the standard choice for structural and wear components as well as dental zirconia blanks. The 8 mol % grade (approximately 13.3 wt % Y₂O₃, 8YSZ) provides a fully cubic structure with maximised ionic conductivity, the key requirement for SOFC and SOEC electrolyte applications.

Commercial specifications

• REACH registered in the 1,000–10,000 t/a tonnage band
• Thermal-spray powders typically supplied at 7–8 wt % Y₂O₃ (7YSZ), with particle size distributions in the 10–90 µm range suited to plasma-spray deposition
• Typical impurity levels for standard industrial grades include Al₂O₃ ≤ 0.25 %, SiO₂ ≤ 0.02 %, and naturally occurring HfO₂ in the 1–2 % range
• Standard industrial packaging is 10–25 kg bags or drums; bulk quantities are available in larger containerised formats depending on grade and form