How is Zirconia Ceramic Cell Phone Panel Produced?

With the advent of the era of 5G signals, intelligent wearable devices are bound to shift from metal to glass and ceramics. Especially, in the mobile phone panel industry, more and more mobile phone manufacturers began to use zirconia ceramic material. So what is the manufacturing process of zirconia ceramic cell phone panel?

Ceramic powder

Microcrystalline zirconium is generally used as the raw material for the shell of 3C products. Zirconia powder is the most widely used ceramic material for the shell of 3C products due to its good appearance treatment effect and the advantages of phase change toughening.

Zirconium Oxide Powder

Ceramic Machining

Ceramic shell molding processes such as mobile phones and smart wear mainly include injection molding, dry pressing molding, and tape casting. Injection molding is similar to plastic injection molding, which is mainly used to produce small and sophisticated ceramic parts with complex shapes. In general, the larger the size, the less advantageous the injection molding; dry pressing mainly produces flat products with high production efficiency; tape casting is an important forming method for thin ceramic materials. The above three molding methods can be used to produce mobile phone panels.

1. Injection molding

Ceramic Injection Molding (CIM) is a new process for ceramic parts manufacturing combining polymer Injection Molding with ceramic manufacturing.

2. Dry Pressing

Dry compression molding is a method to make the powder into a certain shape of the blank body by applying external pressure through the plunger of the press. Due to the moisture content of powder under 7%, the subsequent sintering time is reduced, so the forming efficiency is high and the cost is low, but the density is not uniform.

3. Tape casting

Tape casting is an important forming method for thin ceramic materials with high productivity and automation, but the shrinkage rate of firing is as high as 20-21%. It can be used to prepare high-quality ceramic films with a thickness of 10-1000 microns. Tape casting is used in the ceramic panel of MI 5 mobile phones and the ceramic fingerprint cover of various mobile phones.

4. Debinding and sintering

Debinding is the removal of organic matter from the body of an injection-molded billet by heating or other physicochemical means.

Under the action of high temperature, with the extension of time, the green body finally becomes a hard polycrystalline sintered body with a certain microstructure, which is called sintering. Sintering is a process to reduce the pores in the forming body, enhance the combination of particles and improve mechanical strength.

5. Postprocessing

The panel of 3C products, such as mobile phones and smart wearers, has very high requirements on the surface effect of engineering ceramics, such as smooth and clean surface, precise geometric size, fingerprint protection, and so on. This requires a complex post-processing process, including CNC machining, grinding, polishing, laser /PVD, AF processing, etc.

The above is all about the production process of the zirconia ceramic cell phone panel, I hope it can provide a reference for you. Stanford Advanced Materials supplies high-quality zirconia products to meet our customers’ R&D and production needs. Please visit http://www.samaterials.com for more information.

Zirconia Ceramics: A Hotspot in the Field of Micro-machinery

Zirconia ceramic materials are gradually being widely used in the field of micromachinery, because of its maintain excellent properties such as high-temperature resistance, oxidation resistance, acid and alkali corrosion resistance, hardness, etc.

The development of science and technology has made the miniaturization technology of zirconia ceramic materials become an important issue concerned by all countries, while the equipment tends to be miniaturized, and zirconia ceramics have a broad application prospect in the fields of automobile, medical treatment, aviation, aerospace, military, and environmental detection.

All countries in the world began to invest a lot of money, scientific research forces and too micromechanical system research. Organizations such as the National Natural Science Foundation of the United States and the Department of Defense attach great importance to MEMS(Micro-electromechanical Systems)technology and invest a lot of money in related research; The European Union has set up a multi-functional Microsystems research cooperation agency to strengthen interaction among countries; Japan has formulated the nano-manufacturing plan, the AI(artificial intelligence)technology plan, the microrobot plan, and established the micro machinery center and the micro machinery society; At present, there are more than 60 units engaged in MEMS research in China, and some scientific achievements have been made in the field of sensors and micro-actuators.

micromachinery

Zirconia ceramics are used in micro pressure sensors to detect engine inlet pipe pressure, micro accelerometers for vehicle safety airbag systems, and micro angular velocimeters for wheel sideslip and roll control. Microdevices such as micro pumps, microvalves, micro tweezers, and micro flowmeters applied in zirconia ceramics, and the micro-inertial measurement device, micro-whole analysis system, RF sensor, etc. are used in the military field. Moreover, zirconia ceramic materials can be used as a micro burner, a microreactor, and a pressure sensor at high temperatures and they can also be used as a composite, bone tissue scaffold, and in other biomedical fields because of their good biological solubility.

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Application of Zirconia in Fingerprint Identification

The Fingerprint recognition module is widely used in intelligent portable devices because of its fast, safe, convenient, and other advantages. However, due to the small area of the fingerprint module and complex application environment, it requires high identification sensitivity and speed, which also puts forward very high requirements for fingerprint identification chips and surface protection materials.

At present, there are two commonly used fingerprint identification schemes: pressing on the front of the sapphire cover and coating on the back.

iPhone-6S-Touch-ID

Cost and Performance

In terms of cost and performance, sapphire has high hardness and corrosion resistance, but it has some weaknesses such as high cost and weak anti-falling ability, while the coated back fingerprint recognition scheme has the disadvantages of easy wear and sweat corrosion due to the low hardness of the coating.

Operation

In terms of operation, the two schemes have their own merits. The back fingerprint identification is convenient only for holding the index finger of the hand, while other fingers are inconvenient, and it can’t be used on a plane, it has to be picked up, too, which is not convenient in some special applications scenarios (such as driving). Meanwhile, the positive fingerprint is much smoother for the current hot fingerprint payment.

fingerprint-scanner

Appearance

In terms of appearance, the texture of backside fingerprint recognition is slightly poor, and it is easy to destroy the overall aesthetics of the backside putting fingerprints on the front not only makes the back of the phone more beautiful but also more in line with users’ habits and aesthetics.

Overall, a positive fingerprint is more popular with users, but it costs more. Many years of research have proved that zirconia ceramic cover products can be used for positive pressure fingerprint identification schemes.

The ceramic cover is zirconia ceramic (ZrO2), also known as the zirconium gem. It has superior hardness, toughness, insulation, heat conduction, and other advantages, showing abrasion resistance, fall resistance, corrosion resistance, high-temperature resistance, and other excellent characteristics, which is very suitable for pressing fingerprint identification module cover.

Zirconia ceramic is a cost-effective alternative to sapphire, and the zirconia product has been used in many well-known brands of mobile phones, which has the following advantages.

High hardness

The hardness of zirconia ceramics is 8.5 and that of single crystal alumina (sapphire) is 9, so they are quite similar in wear and scratch resistance.

High permittivity

The permittivity of zirconia is 32-35, which is three times that of sapphire, while all other materials are within 10. This characteristic is beneficial to improve the capacitance difference between the high and low levels of fingerprint identification module, so that fingerprint identification is more sensitive, the success rate is higher, and the speed is faster.

Thin in thickness

At present, the thinnest mass production thickness is as low as 0.1mm under the protection of falling strength of the zirconia protective layer, which is easier to identify than the thinnest sapphire cover with a thickness of 0.3mm. If the thickness is the same as that of sapphire, the strength and fall resistance of zirconia protective coating will be significantly better than that of sapphire.

Good processability

Zirconia ceramics are directly prepared by casting, polishing, and other ceramic processes. Its process is simple and its shape is easy to process, so it costs less than sapphire.

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An Overview of Colored Zirconia Ceramics

Zirconia ceramics, with high strength, high toughness, wear resistance, corrosion resistance and other excellent properties, are widely used in mold, tools, ceramic bearings, electronic components, biomedical materials, and other fields. At present, with the wide application of zirconia ceramics in the field of electronic products, especially as the backboard of mobile phones, its single color has restricted its application and cannot meet people’s requirements on the appearance of structural devices. Therefore, the development of rich colors can greatly expand the application of zirconia ceramic materials in the field, which has broad prospects for development.

Overview of colored zirconia ceramics

With the development of technology, the synthesis methods of colored zirconia ceramics are becoming more and more diversified. The key to its preparation technology is that the color phase (such as CoO, Cr2O3, Fe2O3, etc.) can be evenly distributed in the ceramic matrix. The color zirconia ceramics must have a stable crystal structure, bright and uniform color, high temperature and good chemical stability without damaging its inherent properties.

For colored zirconia ceramics, the capillary force, electrostatic attraction and van der Waals force between particles are prominent due to the small size, large surface area and high surface energy of the particles forming the matrix and colorizing phase. In this environment, nano-powder particles are easily agglomerated into a larger particle body, which leads to a significant decrease in the relatively good physical and chemical properties of nano-complex phase ceramics. Therefore, the agglomeration phenomenon must be overcome to prepare zirconia ceramics with good properties and diverse colors, so that the color phase is evenly dispersed in the ceramic matrix material.

Preparation of colored zirconia ceramics

The preparation methods of color zirconia ceramics mainly include solid phase mixing, chemical co-precipitation, liquid phase impregnation, and high-temperature carburization.

  • Solid-phase mixing

Color zirconia powders were prepared by solid-phase mixing with ball milling technology. It mixes oxide particles such as the colorant and mineralization agent with stable zirconia nanometer powder in a certain chemical proportion and grinds them into balls. Solid particles are refined in this process, resulting in micro-cracks, lattice distortion, and surface energy increase that are conducive to the realization of the low-temperature chemical reaction.

Black zirconia ceramics are used in watch straps

  • Chemical co-precipitation

After the solution of a zirconium salt, stabilizer salt and colorant ion salt is mixed, hydroxide or carbonate precipitation is generated by the reaction with alkali or carbonate, and then the zirconia composite powder is obtained by heating and decomposition. In coprecipitation, metal cations in a solution precipitate together to form a mixture due to an excess of precipitants. Under special circumstances, the composite oxides or their precursors that are required to be deposited must conform to a certain stoichiometric ratio, and cations are required to generate precipitation in a certain proportion.

  • Liquid phase impregnation

Liquid phase impregnation will firstly extract and degrease zirconia ceramic blank with connected pore structure after injection molding and then place it in a solution containing chromophore ions for impregnation. The colorized ions infiltrate into the surface of the billet through the pores of the solution, and the depth of infiltration is controlled by the length of infiltration time. In addition, the blank body obtained by water extraction and degreasing is directly used for infiltration, because the blank body after water extraction and degreasing will form a uniformly connected void structure, which facilitates the uniform distribution of chromophore ions in the blank body. Uniform color zirconia ceramics can be prepared only if they can be soaked completely.

  • High temperature carburizing/nitrogen

High-temperature carburizing is mainly used to prepare black zirconia ceramics. The technological process is to process zirconia ceramic into a blank, normal degreasing, dewaxing, at low temperature without protective atmosphere element burning treatment, and then the processed zirconia green blank under vacuum protection conditions for high-temperature sintering. Graphite crucible is used to place the workpiece during sintering, and graphite paper is placed on the workpiece surface. The black coloring of zirconia ceramics was realized by graphite infiltration into the zirconia surface at high temperatures.

Applications of color zirconia ceramics

  • The backplate of a mobile phone

Zirconia ceramic used in mobile phone backplate has no interference, no magnetic, strong reception signal, as well as color diversity, besides, it can also be used for fingerprint identification module ceramic cover plate.

Zirconia ceramics are used in the back plate of mobile phone and the ceramic cover plate of the fingerprint recognition module

  • Smart wearable appearance parts

Zirconia ceramic material has the advantages of scratch resistance, scratch resistance, no shielding, warm and moist hand texture, good corrosion resistance and bio-compatibility. It is applied to intelligent wearable appearance parts.

Smart wearable appearance parts

  • Ceramic knives

Zirconia ceramic knives have excellent characteristics such as ultra-high strength, abrasion resistance, sharp edge, no rust, no odor, and durability.

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Main Factors that Affect the Performance of Ceramics

The main raw material of zirconia ceramics is high purity zirconia powder, and its performance and content have a great impact on zirconia ceramics. Besides that, the properties of zirconia ceramics are affected by other factors. In order to prepare high-performance zirconia ceramics, we should control the main influencing factors, including raw material size, molding method, and sintering.

Forming method

Zirconia ceramics with low porosity and high density have excellent jointing properties. High density means that the grains in the ceramic body are closely arranged, and it is not easy to form a destructive breakthrough point when subjected to external loads or corrosive substances.

The forming method is the key to obtaining the calcium density of the ceramic embryo body. Zirconia ceramics are usually formed by means of dry pressing, isostatic pressing, and hot die-casting. Different methods have different characteristics and have different effects on sintering properties as well as the microstructure of curing rate ceramics. Generally, grouting and hot die-casting are the main technologies for products with complex shapes, while dry compression molding can be adopted for products with simple shapes. Generally speaking, the density of dry-pressed products is better than that of hot-die-cast products.

The particle size of the raw material

The particle size of raw material has a great influence on the properties of products. Only when the raw material is fine enough can the final finished product be fired into a microstructure, which makes it have good wear resistance. The finer the zirconia powder particles are, the more active they are and the sintering can be promoted.

Due to the difference between corundum and glass phase linear expansion coefficient, the stress concentration at the grain boundary can reduce the risk of cracking. The fine grain can also hinder the development of micro-cracks, and it is not easy to break into transgranular, which is conducive to improving fracture toughness and abrasion resistance.

Sintering

Sintering of ceramic is the densification process of raw ceramic at high temperatures. With the increase in temperature and time, the adhesion between powder particles and the strength of sintered body increase, the aggregation of powder particles becomes a strong polycrystalline sintered body with a certain microstructure, and the required physical/mechanical properties of products or materials are obtained. The densification rate and the final structure of the sample often reflect what kind of heat treatment process it has gone through.

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7 Methods to Toughen the Zirconia Ceramics

Zirconia ceramics are characterized by unique physical and chemical properties such as high hardness, low thermal conductivity, high melting point, resistance to high temperature and corrosion, chemical inertia and amphoteric properties. As a special ceramic material, zirconia has a broad application prospect in electronics, aerospace, aviation, and nuclear industries.

At present, the toughening methods of ceramics mainly include phase transformation toughening, particle toughening, fiber toughening, self-toughening, diffusion toughening, co-toughening and nano toughening.

  1. Phase transformation toughening

The toughening of the phase transition refers to a phase transition of t-ZrO2 of the metastable quadrilateral phase under the stress field at the crack tip, then the compressive stress is formed on the crack, which hinders the crack growth and plays a role of toughening.

Besides, external conditions (such as laser shock, fatigue fracture toughness, low temperature, grain size and content, critical transformation energy, etc.) have great influence on the toughening of zirconia ceramics. If the stress and volume produced by the phase transition are large, the product is prone to fracture. Therefore, the influence of external factors on the toughening of zirconia ceramics should be avoided in the production process.

  1. Particles toughening

Particle toughening refers to adding ZrO2 ceramic powder as a toughening agent. Although the effect is not as good as whisker and fiber, there is still a certain toughening effect if the type, size, content and matrix materials are selected properly. The advantages of particle toughening are simple and feasible, and the toughening will bring about the improvement of high-temperature strength and high-temperature creep property. The toughening mechanism of particle toughening mainly includes grain refinement and crack turning to the bifurcation.

  1. Fibre toughening

The toughening principle of fiber and whisker is that the closed stress is applied to the crack surface due to the deformation of crystal close to the crack tip, the external stress of the crack tip is offset, and the passivating crack growth is achieved, so as to play a toughening role. In addition, when the crack grows, the pulling out of the column crystal also overcomes the friction force, which also plays a role in toughening.

  1. The self-toughening

Due to the existence of columnar crystals, the fracture process of zirconia ceramics can cause the crack to deflect, change and increase the crack growth path, thus passivating the crack to increase the crack growth resistance, thus achieving the purpose of toughening.

  1. Dispersion toughening

Diffusion toughening mainly refers to the toughening of tetragonal ZrO2 particles to ceramic matrix. Besides the phase change toughening mechanism, there is also the diffusion toughening mechanism of the second phase particle. Before the crack propagation, the internal residual strain energy of the ceramics must be overcome, so as to achieve the purpose of toughening.

  1. Microcrack toughening

Microcrack toughening refers to adding ductile materials to the stress tip of the crack to generate microcracks to disperse the stress, reduce the force of the crack forward, and thus increase the toughness of the material. When phase transition occurs, residual strain energy effects and microcracks often occur. Therefore, the effect of phase transition and toughening is remarkable.

  1. Composite toughening

Composite toughening refers to the application of several toughening mechanisms in the actual toughening process of ZrO2 ceramics, so as to improve the toughening effect of ZrO2 ceramics. In the practical application process, the specific toughening mechanism is selected according to the different properties of zirconia ceramic materials to be prepared.

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Can Zirconia Ceramics be used as Wearables?

Zirconia ceramics enter the consumer electronics represented by mobile phones in three subdivisions.

  • The main application area is the back cover of the mobile phone, which is mainly used to upgrade and supplement plastic, glass and metal materials.
  • The second is the patch or the case of the wearable device used for fingerprint identification, which mainly benefits from the increase in the installed rate of the fingerprint reader and the replacement of sapphire.
  • Finally, it is used for small structural parts such as lock screen and volume button, which is a continuation of the ceramic button business in the era of the functional machine.
ZrO2 Back Cover of the Mobile Phone
ZrO2 Back Cover of the Mobile Phone

In contrast, zirconia has a density of 6 grams per cubic meter, the heaviest of all materials. Fortunately, zirconia ceramics can be controlled by thickness, keeping the total weight to a level lighter than glass. Besides, the back set of fine CNC processing required time and high cost because of the superior wear-resisting performance of ceramics. As a result, zirconia has exploded more quickly in areas such as fingerprint recognition, wearable devices and the back cover of mobile phones, where it is more cost-effective.

Apple Watch

As early as April 2015, the Apple Watch went on the market and used zirconia ceramic material as the rear cover appearance for the first time, which brings the wearables’ ceramic facade to a climax. Compared with metals and plastics, zirconia ceramics are wear-resistant and skin-friendly, making them more suitable for use on wearable devices. In addition, the airtightness and waterproof of wearable devices determine that most of them adopt wireless charging mode, and the ceramic material is used as the rear cover with small signal shielding, which is obviously superior to the metal material.

Due to the aesthetic and waterproof considerations, most wearable devices have the function of wireless charging, and the wireless charging scheme of the non-metal back shell is easier to design. From the perspective of shielding efficiency, zirconia ceramics, as a non-metal material, have no shielding effect on electromagnetic signals, and will not affect the internal antenna layout at all. Therefore, it can be conveniently shaped into a whole, instead of making an ugly segmented structure like aluminum magnesium alloy. Arguably, Apple’s Apple Watch led the trend of zirconia ceramics being the back cover of wearables.

Apple Watch

Wearable devices

In addition, zirconia ceramics also have the following advantages as wearable devices. As mentioned above, zirconia ceramics have higher dielectric constants that make fingerprint scanners work more sensitively and cost significantly less than sapphires. The Mohs hardness of zirconia ceramics is around 8.5, which is very close to that of sapphire 9. Given all the advantages of zirconia ceramics, it is expected that it will become the preferred rear cover material in the field of wearable devices in the future.

Stanford Advanced Materials supplies high-quality zirconia ceramics and related machining products to meet our customers’ R&D and production needs. Please visit http://www.samaterials.com for more information.

How did people come up with Zirconia Ceramics for Tableware?

Most people think they are very strange to zirconia ceramics and have little contact with them, but in fact, we only need a few examples to make it clear. The simplest examples are the utensils we use in our daily lives, such as zirconia ceramic chopsticks, zirconia ceramic soup spoons, zirconia ceramic teacups, and so on, all of which are made from zirconia ceramics.

But how did people come up with this material for tableware? This is because traditional ceramics have problems such as poor resistance to fall and durability, and the appearance and application of zirconia ceramics completely solve these problems. This special material is not only resistant to acid, alkali, and rust, but also has good environmental protection. It is the ideal choice of tableware materials.

Zirconia ceramic chopsticks

Zirconia ceramics are by far the most resilient of ceramic materials, so you don’t have to worry about breaking them when you make your cutlery. Besides, it has an excellent high-temperature solid electrolyte, oxygen ions can also pass through at a high temperature, which is a very special ceramic material. The following is a special case of zirconia ceramic knife to explain in detail the application of zirconia ceramics in kitchen utensils.

Zirconia ceramic knife is made from zirconia ceramic material which belongs to nonmetal material. Since the material purity and particle size were controlled, and various carbides, nitride, boride, and oxides were added to improve their properties, not only did the bending strength of the zirconia ceramic knife increase to 0.9~1.0GPa, but also the fracture toughness and impact resistance were greatly improved. In recent years, the application range of zirconia ceramic knives has been expanding, from high-tech fields such as aerospace to the industrial ceramic knife.

Characteristics of zirconia ceramic knife

Clean

The ceramic knife is designed in a close manner with no gaps and pores, no sticky bacteria and foreign body, and will not become a breeding ground for bacteria. The super antibacterial function of the ceramic knife is very suitable for cutting food which can be eaten directly.

Zirconia ceramic knife

Resistance to food oxidation

The ceramic knife will not react with any food, maintaining the original taste of the food, allowing you to fully experience the enjoyment of the delicious food. By the way, ceramic knives are very suitable for cutting raw fish, fruits, vegetables, boneless meat, and cooked food.

Healthy and Eco-friendly

The ceramic knife, which does not emit metal ions, has excellent non-metal properties, making it never rust. Besides, the healthy and environmentally friendly ceramic knives are resistant to various acid-base organics, and will not be corroded by acids and oils in fruits and vegetables. It is non-toxic, pollution-free, non-oxidizing and non-rusting.

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Is the Zirconia Full-porcelain Teeth Safe?

Zirconia is an excellent high-tech biological material with good biocompatibility that is superior to various metal alloys, including gold. Zirconia has no irritation or allergic reaction to the gingiva, and is suitable for oral application, avoiding allergic, stimulative, and corrosive reactions of metal in the oral cavity.

Excellent mechanical properties

The zirconia full porcelain dental material has a winding strength greater than 900MPa, so it can also be used to repair the posterior tooth and the all-ceramic bridge with more than 6 units.

Good biocompatibility

In the latest clinical evaluation report of CRAI, a U.S. clinical research association, it was found that the zirconia all-ceramic crown itself had no metal, and the restoration of the zirconia all-ceramic crown could exclude the metal allergic reaction and have good biocompatibility. Therefore, zirconia all-ceramic crowns are superior to various metal alloys in terms of biocompatibility, including gold materials.

Zirconia Crown

Safe non-metallic materials

At present, zirconia is the only mineral in the natural world, which does not contain any metal, and it is safer after medical clean processing.

No obstruction to the X-Ray

If cranial X-ray, CT, and MRI examinations are needed after inserting the zirconia porcelain teeth, the dentures do not need to be removed in the future, because the zirconia porcelain teeth do not have any obstruction to X-ray, so a lot of trouble is avoided.

High intensity and density

Zirconia is widely used, especially in high-precision instruments, such as aviation equipment, because of its ultra-high-strength and density. Among them, the unique resistance to rupture and the strong firmness after rupture can be made into all-ceramic Bridges of more than 6 units, thus solving the problem that all all-ceramic systems cannot be long Bridges. Therefore, they are favored by doctors and patients.

Zirconia full porcelain teeth

Perfect color

Due to the white color of the base crown of structural ceramics, the neck will not become dark for a period of time after the insert, which solves the extremely difficult problem of the metal crown.

Healthy biomaterials

Zirconia is an excellent high-tech biological material with excellent biocompatibility and no irritation or allergic reactions to the gums. It is very suitable for the mouth.

PFM (porcelain fused to metal) is accepted by most patients for its good strength, but it has its fatal disadvantages. The metal base of low-end porcelain teeth is easy to oxidize and form gray oxides. When scattered and deposited at the edge of the gingiva, the gingiva will turn gray and affect its appearance. At the same time, it has a strong stimulation effect on the gingiva, and some patients may also have gingiva swelling, bleeding, allergy, and other symptoms, which is difficult to meet the clinical requirements. High-end metal porcelain teeth (gold alloy) are expensive without these drawbacks.

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How to tell the Zirconia from Diamonds?

Diamond is the product of adamas finishing, which is the hardest and simplest gemstone in the world. It is a natural crystal with a cubic structure made of carbon. The bigger the diamond, the rarer it is. Diamond often contains 0.05%-0.2% impurity elements, among which N and B are the most important. The pure diamond is colorless and transparent, which presents different colors due to the mixing of trace elements.

Natural diamonds are expensive due to their scarcity, especially the larger ones. However, artificial diamonds (synthetic diamonds) are difficult to achieve large size gemstones. Generally, synthetic diamonds are used in cutting and polishing tools. Therefore, in order to meet the design needs of jewelry and some products, there are usually some substitutes, such as glass, artificial spinel, artificial sapphire, zircon, scheelite, strontium titanate, cubic zirconia and so on. Among them, cubic zirconia is very close to diamond in terms of its optical and hardness properties and is the most common diamond substitute.

The cubic zirconia was first developed by the Soviets, also known as Soviet Stone. Cubic zirconia in cubic crystals is rare in nature and is usually synthesized artificially. Synthetic cubic zirconia is a hard, colorless and optically immaculate crystal, and it has been a replacement for diamonds since 1976 because of its low cost, durability and its resemblance to diamonds. Cubic zirconia is known as a “fake” diamond or CZ diamond. The following is a brief analysis of the difference between diamonds and “fake” diamonds and how they are identified.

Difference in hardness

Natural diamonds have a Mohs hardness of 10 and are difficult to process, and the cubic zirconia has a Mohs hardness of 8.5 to 9.0, while quartz sand is 7 and stainless steel is only 5.5. Therefore, the treatment of gem-level cubic zirconia can meet the requirements of daily use and is easier to process.

Differences in dispersion

The dispersion of cubic zirconia was 0.060, which is higher than that of diamond, so cubic zirconia looks more brilliant than diamonds.

The index of refraction

Cubic zirconia has a refractive index of 2.176, which is slightly lower than diamond’s 2.417. Depending on the refractive index, cubic zirconia cuts slightly differently from a diamond, which can be seen under a magnifying glass.

Color

Completely colorless diamonds are very rare, and usually, they are pale yellow. However, the cubic zirconia can be made into diamonds of the highest grade, or D-grade color. A variety of trace elements can also be added to the cubic zirconia to render it in different colors to meet customers’ demand for colored gems.

The crystals of different colors can be obtained by adding different metal oxides to the raw materials. For example, cerium: yellow, orange, red; chromium: green; neodymium: purple; erbium: pink; titanium: golden brown.

Specific gravity

Cubic zirconia is 1.7 times heavier than a diamond, so they can be distinguished by differences in specific gravity, but can only be used to separate unencrusted gems.

The heat-transfer capability

The thermal conductivity of cubic zirconia and diamond are two extremes. Cubic zirconia is a good insulator and can be used as an insulator for jet engines, while diamond is one of the best heat conducting bodies, its heat-conducting ability surpasses copper.

Stanford Advanced Materials supplies high-quality zirconia products to meet our customers’ R&D and production needs. Please visit http://www.samaterials.com for more information.