Case solved! Xiaomi Longjing Ceramic: ceramic phase, glass core

Author | Yunpeng

Editor | Xin Yuan

Porcelain is touched? Recently, the issue of "whether Xiaomi Longjing Ceramics is glass" has become the "biggest melon" in the digital technology circle, attracting great attention from industry professionals and consumers.

The discussion on materials science of ceramics and glass has also "involved" manufacturers such as Apple, Huawei, and Honor, with terms such as "super ceramic crystal glass", "crystalline glass", "crystal", and "glass ceramics" Beginning to be recognized by people, a popular science popularization of mobile phone materials swept the technology circle.

Zhixixi reported on March 6 that at 1:20 this morning, UP Shengli Wenjue in the B Station Technology Zone officially released the "Grand Finale" video about Xiaomi Longjing Ceramics.

Based on the final test report of the laboratory, he concluded: "Xiaomi Longjing Ceramics is glass."

To be more precise, Xiaomi Longjing Ceramics is a kind of crystallized glass with a crystal content of up to 88%. Crystals are the main microstructure of ceramics.

Laboratory test report

According to the authoritative book "Introduction to Ceramics" in the field of ceramics, Xiaomi Longjing Ceramics can belong to the broad classification of ceramics.

This shows to a certain extent that Xiaomi has its origin in naming its back panel material "Dragon Crystal Ceramic".

The UP also admitted that Xiaomi’s dragon crystal ceramics has the highest crystallinity among the glass-ceramics, so Xiaomi will definitely need to spend more manufacturing time and manufacturing costs. Xiaomi’s technology research and development strength is worthy of recognition.

Comparison of cross-section materials of different models

An unprecedented discussion about the back cover materials of Xiaomi mobile phones that lasted for 5 days, 7 hours and 17 minutes has finally come to an end.

Why did it take so long from the time I started doing the experiment on Thursday afternoon to today? The UP gave an answer that no one expected: force majeure - the laboratory is on holiday! (No one wants to make testers work overtime [dog]).

As we all know, Xiaomi is one of the earliest domestic Android phone manufacturers in the research and development of ceramic materials for mobile phones. The ceramic version of Xiaomi’s flagship phone has always been a highly requested version by rice fans. For a Chinese listed technology giant, whether the "ceramic" materials used in its products are "glass" is a very important issue of principle.

Besides, now is a critical period for Xiaomi mobile phones to impact the high-end market.

This is why as soon as the news came out, the technology circle immediately "exploded".

In fact, with the development of mobile phone material technology, the integration and complementation of the advantages of various materials has become a major trend. On February 29, Wang Hua, general manager of the public relations department of Xiaomi Group, retweeted relevant bloggers’ remarks about the Xiaomi Longjing glass incident on Weibo.

The blogger believes that Xiaomi Longjing Ceramic is a kind of glass ceramic, and glass ceramic is a "branch of advanced ceramics", inheriting the high temperature resistance, corrosion resistance, high strength, high hardness, chemical stability, and low expansion coefficient of ceramics , taking into account the light transmittance of the glass, Xiaomi clearly stated at the press conference that Dragon Crystal Ceramics is "polycrystalline ceramics", which is reasonable.

In fact, the super ceramic crystal panel used by Apple iPhone 15 Pro is translated as "Ceramic Shield front" on the English official website. Ceramic has a related interpretation of "ceramic" in English.

The industry has paid a lot of attention to this matter, partly because of the point at which the incident occurred.

On February 3 this year, Lei Jun revealed on Weibo that in order to go all out to develop Xiaomi's car business, Lu Weibing, who was originally responsible for the Redmi brand, will switch to leading Xiaomi's mobile phone business line. At the same time, Wang Teng will take over the management of the Redmi business. . Such high-level adjustments not only show Xiaomi's high commitment and expectations for automobile projects, but also release an important message: Lei Jun will concentrate on automobiles.

Lei Jun posted on Weibo on February 3-4th

In the early stages of Lei Jun making important adjustments and starting to focus on car development, the industry will inevitably pay higher attention to the trends of Xiaomi's mobile phone business.

According to supply chain information, orders for the entire Xiaomi Mi 14 series have been increased by 40%. Wang Hua, General Manager of the Public Relations Department of Xiaomi Group, also mentioned in forwarding Weibo posts of other Xiaomi executives that the Xiaomi Mi 14 Pro Titanium Special Edition is also in the replenishment stage. . Although the naming of product materials has caused some controversy, it is still a fact that the sales of the Xiaomi Mi 14 series are booming.

Although the Xiaomi Longjing ceramic incident has basically come to an end, research on mobile phone materials continues. From plastics and metals to glass and ceramics, technological breakthroughs in mobile phone materials will still be one of the important areas of mobile phone technology innovation for a long time.

As of 9 am Beijing time, Xiaomi has not responded to the latest video posted by this UP.

(The relevant pictures cited in this article are from the videos published by UP)

1. Five professional tests to find the answer, the definition of ceramics becomes the key

In the "Grand Finale" video, the UP gave the results of the final test report of the experiment A more detailed explanation was given.

Based on five professional tests: SEM, XRD (refinement), XRF, flame photometry, and chemical titration, the laboratory produced a test report. A brief summary shows that the crystal content of Xiaomi Longjing Ceramics is about 88% , the amorphous content is about 12%.

According to the report, the highest proportion is lithium feldspar, with a content of 43% ± 2%, lithium disilicate ranks second, with a content of 34% ± 2%, and lithium silicon aluminum ranks third. The stone content is 11%±2%. In addition, dragon crystal ceramics contain 12%±2% amorphous phase and other components. The amorphous phase is mainly the glass phase.

Simply put, Xiaomi Longjing Ceramics has the same crystal structure as ceramics and the same amorphous structure as glass.

In fact, the main source of controversy comes from what is the definition of "ceramics"? What kind of materials can be defined as ceramics?

According to the video, in the academic field of ceramics, ceramics are "products formed by sintering powdery raw materials." However, in the field of mobile phones, the ceramics that the public understands usually refer to "zirconia", which is also the current ceramic back of mobile phones. The main material of the board.

In the book "Smart Terminal Ceramics", the author Xie Zhipeng wrote: "The most commonly used smart terminal ceramics are high-strength and high-toughness nano-zirconia ceramic materials..."

Due to Xiaomi Longjing Ceramics The back panel can be classified as "transparent", so the core thing this UP wants to find out is whether Xiaomi Longjing Ceramic is a transparent ceramic or a glass-ceramic.

He found that transparent ceramics and glass-ceramics have different definitions in textbooks. In most textbooks, transparent ceramics belong to ceramics, and glass-ceramics usually appears in textbooks on glass classification.

It is mentioned in the textbook "Inorganic Non-metallic Materials" that glass-ceramics, also known as microcrystalline jade or glass ceramics, is glass that has been uniformized through heat treatment, light irradiation or chemical treatment under the action of a catalyst or crystal nucleation agent. A large number of tiny crystals are precipitated to form a multi-composite material that combines dense crystal phases with glass.

So, inside the glass-ceramics, there are both crystal and amorphous glass phases. Therefore, it is very critical whether the amorphous phase in the experimental test results is the glass phase.

During the experiment, they compared Xiaomi Dragon Crystal Ceramics with the super ceramic crystal cover of iPhone 12. They found that without using hydrofluoric acid to corrode the glass phase, neither could photograph the cross section with an electron microscope. of crystals.

After using hydrofluoric acid to etch away the glass phase, both can take pictures of clear microcrystals at the cross section.

The reason is that glass and ceramics are prepared in different ways, so even though ceramics and glass both have a glass phase, the glass phase in the glass serves as a binding phase and is evenly distributed throughout the material. These glasses meet Wraps microcrystals so that electron microscopes cannot photograph crystals.

However, in traditional ceramics, the distribution of crystal phase and glass phase is most likely to be uneven, so even without hydrofluoric acid corrosion, crystals can be directly found on the cross section with a high probability.

Finally, the UP concluded that Xiaomi Longjing Ceramics is a type of glass-ceramic.

So finally, is it possible that Xiaomi Longjing Ceramic, this kind of glass-ceramic, is a special kind of ceramic?

In the field of ceramics, "Introduction to Ceramics" is one of the most authoritative books, which defines ceramics as the art and science of manufacturing and applying solid products composed of inorganic non-metallic materials as basic components . From this perspective, Xiaomi Longjing Ceramics can belong to the general classification of ceramics.

2. Looking for the source, the hardness test became the starting point of the controversy

So as a "big melon" spread throughout the entire technology circle, what is the beginning and end of this incident? It all started when this UP got the Xiaomi Mi 14 Ultra he just bought on the afternoon of February 28.

This UP conducted a Mohs hardness test on the dragon crystal ceramic back cover of Xiaomi Mi 14 Ultra. It showed scratches starting from level 6 and level 7. Grade scratches are more obvious.

This performance is closer to the crystallized glass tested by this UP before. Generally, the Mohs hardness of zirconia, the main component of ceramics, is around 7.5.

This UP also conducted a hardness test on the back cover of the Huawei Mate 60 RS Extraordinary Master Edition. The back panel is also advertised as ceramic material, and the actual test The ceramic backplate is scratch-proof at level 7.

As a result, this UP had doubts about the actual material of the Xiaomi Mi 14 Ultra dragon crystal ceramic back cover, and later tested the dragon crystal through a crystal hardness test pen The crystal ceramic back cover was tested, and it also showed scratches at level 6.

For a time, the saying "Xiaomi Longjing Ceramics is glass" began to ferment rapidly in the market.

There are also many jokesters on the Internet:

There are also many "mathematicians" who have begun to use formulas to prove ：

The joke is a joke, what are the facts? Is the Xiaomi Longjing ceramic back cover ceramic or other materials? In order to clarify this matter, this Bit UP conducted further disassembly and analysis of the back cover of the phone, and released a video titled "Is the Dragon Crystal Ceramic of Xiaomi Mi 14 Ultra Ceramic?" at around 3 a.m. on February 29, in which he discussed the incident. The detailed beginning and end, as well as what I will do next, are described in more detail.

After discovering the problem during the hardness test, the UP removed the back cover of the phone and scratched the inside of the back cover with metal, and found The blue coating has peeled off, and the material of the back cover is "transparent".

Since glass is a kind of amorphous crystal and itself is transparent, all mobile phone back covers are colored internally. However, the ceramic formed by sintering itself shows its proper color and is not transparent.

In addition to transparency, the UP also measured the weight of the back cover. The measurement results showed that its weight is close to that of the glass mobile phone back cover, both of which are about 26 grams, while the traditional ceramic mobile phone back cover The weight of the cover is usually above 43 grams.

Of course, the results of the transparency, weight and hardness tests do not necessarily mean that it is glass, but to a certain extent, it shows that Longjing ceramics is unlikely to be Conventional ceramic (zirconia) material, for this reason the UP made an appointment with the laboratory for further composition analysis.

Why do we need to analyze the ingredients? In fact, the broad academic definition of ceramics is an inorganic material composed of crystals, so if Xiaomi finds a transparent crystal material, it can also be called "ceramics."

At present, "transparent ceramics" are mainly aluminum nitride, aluminum oxide, iridium oxide, etc. These materials are generally used in the military field, or high-power lasers The transmitting end of the transmitter has a higher cost.

Aluminum oxide is relatively commonly used commercially and is also called "sapphire". This UP believes that the possibility of Xiaomi Longjing ceramic back cover being made of sapphire is not high.

Glass and ceramics are both silicate materials. The main difference is that the content of various elements is different, and the "crystal phase" is also different. The main component of glass is silica, which is basically amorphous, while ceramics are crystalline.

The crystal steps of the crystal are closely arranged and closely arranged. There is basically no "glass phase", and glass is basically a glass phase. Even manufacturers such as Apple, Huawei, and Honor are popular Ceramic glass also has only a very small amount of "microcrystalline phase".

The video mentioned that in fact, as early as the launch of the mobile phone, the UP became curious about the dragon crystal ceramic on the back cover of Xiaomi Mi 14 Ultra. Xiaomi said at the press conference that dragon crystal ceramics have the warm texture of ceramics, are stronger and more wear-resistant, and are 50% lighter than ordinary ceramics.

More importantly, Xiaomi said at the press conference that dragon crystal ceramics are polycrystalline ceramics composed of tiny crystals through a heat treatment process. But ceramics are inherently crystals, which confused him.

Similar descriptions of dragon crystal ceramics appear more often in the promotion of glass-ceramics, such as the "super porcelain crystal glass" back cover of Apple's iPhone. It is a type of glass-ceramic.

Apple’s partial description of the production process of the iPhone’s ultra-ceramic glass back cover

This UP has previously published about Apple The iPhone 12 has conducted a detailed back cover material analysis and provided detailed data on the proportions of chemical elements in the back cover.

Microscope picture of iPhone 12 back cover

At that time, iPhone 12 used a "super ceramic crystal glass" back cover for the first time. Manufacturers such as Honor in the Android camp also have similar "super porcelain crystal" back cover products, so super porcelain crystal glass has become a hot topic in the industry at that time.

At the end of the video, the UP emphasized that before the laboratory results come out, it is still not 100% sure what the Xiaomi Longjing ceramic back cover is. Not glass, so lab results become critical.

At 14:36 ​​pm on February 29th, the experiment officially started!

UPPut the Xiaomi Longjing ceramic glass back cover into the XRD tester (X-ray Polycrystalline Diffractometer) for testing. This type of equipment is often used to study the internal microstructure of matter.

Some results were obtained quickly, and UP soon released a new video at around 4:20 pm on February 29.

Judging from the test results of the surface layer of the back cover by the The main crystal of the iPhone’s ultra-ceramic glass back panel.

Xiaomi Longjing Ceramics A piece of crystallized glass with lithium feldspar crystallized through a melting process to precipitate lithium feldspar crystals.

Interestingly, UP also conducted the same test on the dragon crystal glass on the front panel of Xiaomi Mi 14 Ultra. The test results showed that the dragon crystal glass front The wave phase of the panel and the Dragon Crystal ceramic back cover are almost the same.

The subsequent UP will cut the back cover, grind it into powder, and further analyze the internal components. They will use flame photometry, X-ray fluorescence spectrometer (XRF) testing, SEM electron microscope analysis and other methods to test the dragon crystal ceramic back cover.

Immediately afterwards, at 17:54 pm on the same day on the 29th, the UP released the second test video.

In the second test video, UP conducted another hardness test on the Xiaomi Longjing ceramic back cover in the Vickers hardness tester. The Vickers hardness test is more accurate than the Mohs hardness test.

According to the test report, the data of the white ceramic back cover of Xiaomi 11 Ultra is 1344-1392HV, the data of Honor Magic3 Ultimate Ceramic Back Cover is 1414-1446HV, the data of Honor Magic6 glass back cover is 938-1195HV, and the data of Xiaomi Mi 14 The data for the Ultra Dragon Crystal ceramic back cover is 796-915HV, and the data for the Dragon Crystal glass front panel is 700-919HV.

This further proves the conclusion in the first test video: the material of the dragon crystal glass front panel and the dragon crystal ceramic back cover are basically the same, and they are most likely a piece of crystallized glass with lithium feldspar crystallization.

At 19:35 on March 1, the SEM electron microscope test results and preliminary ingredient content results were announced.

Judging from the cross-sectional electron microscope picture of the Xiaomi Longjing ceramic back cover, this cover has spherical microcrystals, a clear crystallization process, and the crystal content is higher than other products that UP has tested before. Crystallized glass.

Judging from the composition analysis results, there are two crystals with the highest content inside the Xiaomi Dragon Crystal ceramic back cover: lithium feldspar (Li[ALSi4O10]) and lithium disilicate (Li2Si2O5), but the specific ratio has not yet been determined confirm.

3. "Official": Whether it is ceramic depends on whether it has crystals. Glass ceramics is a branch of advanced ceramics

Of course, when the UP raised questions and conducted experiments, Xiaomi also made some "non-positive responses" .

Wang Hua, General Manager of the Public Relations Department of Xiaomi Group, retweeted relevant bloggers’ comments on the Xiaomi Longjing glass incident on Weibo and gave his own views.

Wang Hua posted: "The significance of science popularization is to increase knowledge for those who want to understand, not to make those who want to set the pace realize their mistakes. People who can't wake up those who pretend to be asleep will change." The cognition of people who can't lead the rhythm, of course, science popularization is not used to argue about winning or losing."

Look specifically at this Weibo post forwarded by Wang Hua. The blogger believes that from the perspective of materials science, whether ceramics are necessary. See if there is a crystal structure. It does not mean that the hardness must be greater than 7 to be ceramic.

He mentioned that ceramics are crystalline materials, while glass ceramics have a polycrystalline structure and have the dual characteristics of glass and ceramics. Glass ceramics are "a branch of advanced ceramics". "In addition to inheriting the high temperature resistance and corrosion resistance of ceramics, In addition to high strength, high hardness, chemical stability, and low expansion coefficient, its unique light transmittance allows it to be used in many applications, such as the back cover of Xiaomi Mi 14 Ultra."

At the same time, he believes that it is reasonable for Xiaomi to clearly state that Longjing ceramics are "polycrystalline ceramics" at the press conference.

It is worth mentioning that this blogger quoted Apple’s official promotional page in his blog post. The super ceramic panel used by Apple’s iPhone 15 Pro is translated as “Ceramic Shield front” on the English official website. Ceramic It means "ceramics" in English.

4. From plastics and metals to glass and ceramics, technological innovation in mobile phone materials continues

In recent years, ceramic mobile phone back covers have become increasingly rare, usually only the "super-large cups" of top flagship phones Editions or limited editions will only be used.

Our common flagship phones usually use glass back covers, and some mid- to low-end models use plastic back covers. Overall, glass back cover + metal middle frame is the usual configuration of current flagship phones.

In the era of functional phones, plastic back covers dominate, and they are popular for their cheapness, drop resistance, and impact resistance.

The Samsung Galaxy S6 released in 2015 can be said to be a representative model that ushered in the era of mobile phone backplane glass materials. The glass has a relatively more advanced texture and will not interfere with signals. However, its fragile characteristics also make Manufacturers are constantly developing more "stronger" glass materials.

This is why Apple, Huawei, Honor, Xiaomi and other manufacturers have added more crystals to the glass material through the crystallization process to increase the strength of the glass back cover and screen front panel.

At the same time, the Apple iPhone 7 series released in 2016 immediately made the metal back cover popular, but its weakening of the signal will affect the user experience to a certain extent, and the metal's scratch resistance is also not ideal. Subsequent glass materials still dominate.

iPhone 7シリーズ

セラミックスはガラスとは全く異なる硬度を持ち、コストや加工難易度もガラスよりはるかに優れています。セラミックは硬度が高いですが、耐落下性はガラスほど良くなく、より「脆い」ため、メーカーは構造強度を高めるためにセラミックプロセスを絶えず改良しています。

Xiaomi の最初のセラミック バック カバーの携帯電話は 2016 年に発売され、白と黒で入手可能でしたが、Gionee は 2015 年にセラミック バック カバーを備えた Gionee Tianjian W808 を発売しました。これもまたまさにです。主流ブランドのスマートフォンとしては初めてセラミック製のバックカバーを採用しました。

Huawei Mate 60 RSのレッドバージョンのセラミックバックカバーのように、セラミックス、特にカラーセラミックバックカバーの製造プロセスは非常に難しく、非常にコストがかかり、歩留まりが低いです。ファーウェイは、赤色セラミックの焼結プロセス中に初めて希土類元素であるセリアを添加し、1,400度の高温で焼成し、50以上の製造工程を経て、最終的に内部と内部の両方が均一な完全な赤色セラミックを製造した。外。

Huawei Mate 60 RS Extraordinary Master "Ruihong"

結論: 携帯電話の材料は「複合」技術に向けて開発されていますイノベーションの可能性は依然として有望です

Xiaomi Longjing Ceramics事件を別の角度から見ると、携帯電話メーカーとサプライチェーンメーカーがすでに「互いの強みを学び、補い合う」ことによって携帯電話の素材を繰り返していることがわかります。たとえば、「ガラスセラミックス」では、セラミックスの硬度とガラスの靭性、透明性、光沢を考慮できます。

実際、Appleのチタンミドルフレームはアルミニウムとチタンを融合させたもので、アルミニウムの優れた熱伝導性と高い強度、靭性、耐久性を考慮したミドルフレームとなっています。チタンの軽量化。

今日のスマートフォン テクノロジーの反復は、ソフトウェアとハ​​ードウェアが連携して進歩することを意味しており、スマートフォンがハイエンドに向けて発展し、人々の製品使用体験に対する要求がますます高まっているため、モバイルの革新的な可能性が高まっています。電話材料技術、まだ巨大です。

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