Partially Stabilized Zirconia

Partially stabilized zirconium dioxide (PSZ) is a new non-metallic structural material that combines hardness, reduced fragility, and chemical inertness with high chemical stability in aggressive environments throughout a wide temperature range. PSC is a hard solution of zirconium dioxide with small admixtures of yttrium, alkaline-earth or rear-earth element oxides. Under partial stabilization, zirconium dioxide crystalline lattice partially transforms from tetragonal (cubic) to monoclinic, obtaining a hierarchical micro- or nanostructure.
Highly productive waste-free synthesis technology allows PSZ single crystals to be grown up to 50 mm wide and 180 mm long (link to photo). PSZ performs better than ceramics of the same composition, and high-strength steel or titanium.

Partially-stabilized zirconia (PSZ)
PSZ nano-structure

The new PSZ composition developed by RHT jointly with the Institute of Physics at the Russian Academy of Sciences is characterized by super-high strength under friction and sliding, higher refractoriness, lack of interference in aggressive environments and a number of other advantages over other super-strong ceramic pr metal–based dielectric materials. PSZ articles cut no worse than those of sapphire or diamond, although they cleave much less. Their hardness remains high under elevated temperatures (up to 1400 °С) in acid environments and increase by 70% with -140 °С temperature reductions, while ceramics under high temperatures undergo re-crystallization that alters and worsens its initial mechanical properties. PSZ crystals have increased resistance to acids, alkali, water vapors, are resistant more than other materials to abrasions, and have an abnormally high friction index for steel (-0,04) and wolfram-cobalt alloys (0,08), which is much lower than metal-metal, metal-sapphire and other friction indices.

PSZ crystalls
PSZ in comparison with other crystalline materials
Crystal Chemical composition Density, g/sm3 Thermal expansion index, 106 °С Tensile strength in bending, MPa  Crack resistance (critical coefficient of stress intensity) Micro-strength, GPa
Sapphire Al2O3 3,96 8 300-500 3-4 1900
Cubic Zirconia ZrO2-10 mol% Y2O3 5,7 – 5,9 10-11 200-400 2-4 1200-1600
PSZ ZrO2 - 3 mol% Y2O3 5,99 – 6,08 8-9 500-1200 8-14 1300-1700
Silicon Nitride Si3N4 3,2 3,2 600-900 5-7 1600
Silicon Carbide SiC 3,2 4,2 500-600 3-4 2800

PSZ’s performance allows for the use of it as a material for detailing construction that works under the extreme conditions of high mechanical loads, chemically aggressive environments, elevated temperatures, and lack of lubrication, etc. Due to the micro-domain (10-400A), the nanostructure in PSZ crystals and their high mechanical strength, it is possible to use them to manufacture tools with extremely sharp cutting edges.  PSZ is an irreplaceable material in the manufacture of friction parts in mechanisms, super-hard cutting tools, tooth and bone implants, dyes for wire drawing, as well as other applications. Its ability to change from dielectric to a conductor under heat means it possible to use PSZ as a firm electrolyte. 

Advantages of PSZ as structural material
Melting Temperature, °С ~ 2800
Range of working temperatures, °С -140 - + 2400
Thermal extension index, grad-1 10 – 11*10-6
Thermal conductivity, W/m*K 7,8
Density, kg/m³ 6,06 – 6,08
Tensile strength in bending, MPa 800 - 1200
Tensile strength in compression, MPa 2300 - 3700
Micro-hardness, GPa 11,8 – 15,08
Elastic modulus, GPa 180 - 372
Poisson coefficient 0,26 – 0,36
Tensile relative deformation in bending 0,07 – 0,45*10-2
Crack resistance, MPa*m0,5 0,5 6-15
Wear-out rate 2,5 – 3*10-9
Friction index 0,27 – 0,34

Other advantages    - high resistance to abrasion;
- chemical resistance to aggressive environments  (acids, alkali, metal melts, oxidizing atmospheres under high temperatures);
- bio-inertness;
- radio-opacity;
keeping mechanical properties between a wide temperature range (-140 – 2400 °С);
good dielectric under low temperatures: 20 °С – 2,2*1010 Ω.m
- ion conductor under high temperatures (1000 °С - ~10-2 Ω.м)