Zirconium Oxide: Definition, Advantages, Properties and Applications

November 05, 2024

What is Zirconium Oxide?

Zirconium oxide (ZrO2), known as Zirconia, is one of the most widely studied and used advanced ceramic materials. Compared with other technical ceramic materials, the most prominent feature of zirconium oxide is its extremely high fracture toughness, which makes it have super wear and impact resistance, so it is also named "ceramic steel."

Low thermal conductivity is another unmatched property of Zirconia Ceramics, attributed to its large number of microscopic pores and crystal structure. This unique ceramic crystalline structure gives zirconia an excellent thermal insulation effect.

The Structure of Zirconium Oxide (ZrO2)

Zirconium oxide ceramics have three different phases due to temperature changes, which are:

● From room temperature to 1170℃, it is monoclinic (M-ZrO2) phase;

● Between 1170℃ and 2370℃, it is transformed into tetragonal (T-ZrO2) phase;

● When the temperature is higher than 2370℃, it is transformed into cubic (C-ZrO2) phase.

The three phases of ceramic zirconia can be transformed into each other at different temperatures. The same zirconia ceramic parts with different phases have different sizes, volumes, and mechanical and chemical properties.

Other Advantages of Zirconia (ZrO2)

※ High strength: The compressive strength can reach over 1000MPa, above 5 times that of steel.

※ High-temperature resistance: The service temperature of zirconia can be up to 1000℃

※ High density: It’s a highly dense ceramic material with a density of up to 6.1 g/cm3

※ High hardness: The MoHS of zirconium oxide ceramic hardness is up to 8.5, similar to sapphire

※ Corrosion resistance: ZrO2 doesn’t react with most acids, alkalis, salts, and other chemicals

※ Resistant crack propagation: It’s the real cause of why zirconia zro2 ceramic has superb fracture toughness.

※ Self-lubricity: Zirconium oxide ceramic has a much lower friction coefficient; it’s only ½ of alumina ceramics

※ More Fine Surface: The much higher density and high compactness of zirconium oxide make the texture of the ceramic body fine

※ Resistant to molten metal: ZrO2 ceramic is not easily wetted by liquid metal, so it is highly resistant to corrosion in molten metal.

※ Electrical Insulation: ZrO2 ceramic has a high resistivity at room temperature and can be used as a ceramic insulator, but when the operating temperature exceeds 650℃, it will become an electrical conductor.

Types of Zirconia Materials

Doped with different stabilizers have a significant impact on zirconia materials. According to the main categories of stabilizers, zirconia ceramics can be divided into three types:

1. Yttria Stabilized Zirconia (YSZ)

Zirconium oxide (ZrO2) material is prepared by adding 3 mol of yttrium dioxide called yttria partially stabilized zirconia. YSZ zirconia presents a stable tetragonal crystal structure at room temperature and has high strength, corrosion resistance, high-temperature resistance, good biocompatibility, wear resistance, and good ionic conductivity. With the increase of Y2O3 content, stabilized zirconia ceramics can be transformed from tetragonal phase (partially stabilized) to cubic phase, that is, fully stabilized zirconia (FSZ)

2. Magnesia Stabilized Zirconia (MSZ)

Adding an appropriate amount of magnesium oxide to zirconium oxide can adjust its performance. MSZ has good mechanical strength, thermal stability, and chemical stability.

3. Ceria Stabilized Zirconia (CSZ)

CSZ is a toughened ceramic made using cerium oxide as a stabilizer, uniformly doped in zirconia at a molecular content of 8~16%.

Zirconia Ceramic Material Properties

Electrical

Property	Unit	3Y-TZP	MSZ	CSZ
Dielectric Strength	ac - KV/mm	11.7	9.4	9.8
Dielectric Constant @ 1MHz	(E)	29	28	29.2
Dielectric Loss @ 1MHz		0.001	0.0018	---
Volume Resistivity, 25℃	ohm. cm	1*10¹³	1*10¹³	1*10¹³
Volume Resistivity, 500℃		1*10⁷	1*10⁶	1*10⁶
Volume Resistivity, 1000℃		＜1*10³	＜1*10³	＜1*10³

Thermal

Property	Unit	3Y-TZP	MSZ	CSZ
CTE @ 25~1000℃	10^-6/℃	10.3	10.2	10.3
Thermal Conductivity @ 25℃	W/m.K	2.2	3	3.5
Specific Heat @100℃	J/kg*k	400	400	400
Max. Service Temperature (Non-loading)	℃	500	1200	530

Physical

Property	Unit	3Y-TZP	MSZ	CSZ
Density	g/cm³	≧6.0	≧5.72	≧6.1
Hardness	GPa	12.7	11.8	10
Flexural Strength@25℃	MPa	1200	900	551
Fracture Toughness	MPam^1/2	13	11	15
Tensile strength (3 points) @ 25℃	MPa	690	483	337
Compressive Strength @25℃	MPa	≧2480	≧1750	≧2000
Elastic Modulus	GPa	210	200	180
Poisson’s Ratio	---	0.30	0.30	0.25

Applications of Zirconia Ceramics

1. Typical Applications of YSZ Zirconia

YSZ zirconia is the most widely used of all zirconia categories. Its applications include:

※ Ceramic wear parts

※ Zirconia ball valves and seats

※ Pump seals and shaft bearings

※ Solid oxide fuel Cell (SOFC)

※ Precision ZrO2 ceramic nozzles

※ Ceramic cutting tools and blades

※ Ceramic rollers and guide

※ Ceramic thread and yarn guides

※ Structural ceramic components

※ Oxygen sensor, nitrogen oxide sensor

2. Typical Applications of MSZ Zirconia

※ Engineering applications: mechanical seals, stamping & extrusion dies and wear parts

※ Optical communication device: ceramic sleeves, ceramic capillary, ceramic holders

※ Biomedical science: bone tissue repair materials, biosensors, Fracture internal fixator, and drug carriers

※ Refractories: high-temperature furnace parts, ceramic parts for aerospace engines, and structural materials for spacecraft

3. Typical Applications of CSZ Zirconia

※ Grinding medium: Suitable for grinding all kinds of high-viscosity materials

※ Structural ceramic parts: especially used in high hardness, high-temperature resistance occasions

※‌ Automotive catalytic systems: Ceria stabilized zirconia as a catalyst carrier can improve catalytic efficiency and reduce pollutant emission

Trends

Thanks to its excellent mechanical and thermal properties, chemical inertness, and high-temperature stability, the use of zirconia ceramics will be further deepened and expanded with the innovation of science and technology and the continuous improvement of production processes, moving towards higher performance, more diversified functions, and low cost of the advanced ceramic material.

Author:

Mr. Andy Chen

E-mail:

andy@jinghui0738.com

Phone/WhatsApp:

+86 13760126904