back to article Why next iPhone screen could be made of SAPPHIRE - and a steal...

Man-made sapphire could replace Gorilla Glass as the material of choice for scratch-and-crack-resistant mobile phone screens in the near future, according to a recent speculative piece from MIT Technology Review. According to the research university's mag: Manufactured sapphire — a material that’s used as transparent armor …

COMMENTS

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  1. GreggS

    So

    It's basically clear aluminum?

    Scotty, beam me up!

    1. Pet Peeve
      Boffin

      Re: So

      Yep, and so are rubies.

      I had no idea that the price of silicon had dropped so far. Great article!

    2. Hooksie

      Re: So

      Dammit! Beat me to it. But to be pedantic it's transparent aluminum :)

      Pity Americans can't spell though, should be aluminium.

      1. Big-nosed Pengie

        Re: So

        No - it's you Brits and we Australians who can't spell it. It's aluminum. Some of your scientists decided to change it just so it'd fit in with other "ium"s.

        1. Martin Budden Silver badge
          Headmaster

          Re: So

          No, it's everyone* who can't spell it. It was originally alumium.

          *but especially the Americans, just because ;-)

        2. Ru

          Re: So

          No - it's you Brits and we Australians who can't spell it. It's aluminum

          IUPAC prefer -ium, and its kinda their bailiwick.

          Some of your scientists decided to change it just so it'd fit in with other "ium"s.

          Like molybdenium, lanthanium, tantalium and platinium? Certainly, their efforts at consistency were pretty half-hearted.

    3. Anonymous Coward
      Anonymous Coward

      Re: So

      I have a watch with sapphire glass, from and back. After 14 years still not a scratch to be seen, though the stainless steel case is battle scarred.

  2. jai

    Assuming steady price of Gorillas?

    The assumption here seems to be that Gorilla glass will remain at $3 until and after the sapphire glass industry gets upto speed and reaches the $10 mark? but surely while that is happening, Gorilla glass will continue to get stronger, or it will get cheaper (or both).

    Still, that said, being able say my phone has a screen made of aluminium would be cooler than having one made of gorillas...

    1. wowfood
      FAIL

      Re: Assuming steady price of Gorillas?

      Gorillas > aluminium.

      Have you not seen the cadburys advert with the gorilla playing drums?

      1. Anonymous Coward
        Pint

        Re: Assuming steady price of Gorillas?

        So, you peruse funnyjunk, too?

    2. Anonymous Coward
      Anonymous Coward

      Re: Assuming steady price of Gorillas?

      "Still, that said, being able say my phone has a screen made of aluminium would be cooler than having one made of gorillas..."

      TRAGIC!

      (Fanbois for ya!)

  3. Richard 22
    Thumb Up

    Watches

    My wrist watch has "sapphire crystal glass" - I'd always assumed it was just a coating, but having read this I guess it could actually be the whole glass on the face. Wrist watches are fairly small and round, so I guess would be a good fit for current sapphire ingot manufacturing.

    1. Steve Williams

      True, but...

      Many watches costing over a couple of hundred pounds use solid sapphire glasses, sawn from sausage shaped ingots and then shaped and polished with diamond tools.

      They are quite, but not completely, scratchproof. However they are definitely NOT shatterproof. Any hope of a sapphire crystal surviving hammering or even a significant drop onto concrete is fantasy.

      1. Anonymous Coward
        Anonymous Coward

        Re: True, but...

        Sapphire was used for the windows of Eproms - read only memories that could be erased and reused with ultraviolet light. That brings back memories.

        It is indeed very hard, but as you say, far from shatterproof. Indeed, the harder a material, in general, the more likely it is to shatter on impact with another hard material, because the impact energy is dissipated in a smaller space. A lot depends on the crystal structure.

        1. Anonymous Coward
          Anonymous Coward

          "Sapphire was used for the windows of Eproms"

          You're thinking of is quartz (silicon oxide), not sapphire.

      2. Dave 126 Silver badge

        Re: True, but...

        >They are quite, but not completely, scratch-proof. However they are definitely NOT shatterproof. Any hope of a sapphire crystal surviving hammering or even a significant drop onto concrete is fantasy

        It depends how it is used. A phone screen is thinner than a watch crystal, and it is only the very outer layer that you want to be hard- maybe it could be combined with a more flexible material. I'm thinking of case-hardened spanners, which are hard on the outside, more flexible on the inside so that they don't break when dropped like a drill bit will.

        Many Omega watches use sapphire for the watch crystal but the models used in space used an acrylic-like material... acrylic would be less likely to shatter due to extremes in temperature, and even if it did it would be preferable to tiny shards of sapphire floating around in an enclosed environment.

        Back down on earth, the things likely to scratch a sapphire watch face are harder stones in jewellery, diamond dust (if you've been a diamond blade in a disc cutter) and sometimes the anti-slip coating at the bottom of swimming pools.

        1. goldcd

          I was think along the same lines

          I've got a pretty nondescript Omega I've worn every day for the last ooh ~ decade. Steel bracelet has a nice 'patina' from the casual abuse I've subjected it to, but the glass (which is nicely convex and proud on top) is still absolutely flawless.

          Always wondered why phones didn't just use the same stuff - and now understand - and can't wait until they do.

      3. Mage Silver badge

        Re: True, but...

        Yes, Watch faces have used Sapphire for maybe 50 years. Due to the fact it's much more scratch resistant. Cheap watches used to get quite poorly with scratches in a few months due to softness of the glass.

    2. Anonymous Coward
      Windows

      Re: Watches

      Tissot??

      My T-Touch is Sapphire crystal....

      The titanium surrounding it is well hammered though...

      1. Yesnomaybe

        Re: Watches

        My Omega has a saphire for glass, and I can tell you that when I accidentally hit it with the edge of a spinning grinding disc on an angle-grinder, it saved my wrist from unsightly abarasion, and although metal was smeared accross the glass, this came off, and there was no scratch in the saphire. Incredible stuff, I'll be wanting a phone with that stuff as a screen.

        1. Anonymous Coward
          Anonymous Coward

          Re: Watches

          This could explain why my Casio waveceptor is still useable after being variously wacked into brass door handles and steel scaffold poles. And I'd wondered why metal was leaving marks on the "glass" that just polished off. It's predecessor was retired after an encounter with the bottom of a swimming pool.

          Maybe they should stop wasting time on sapphire, and move straight to make mobile phone screen out of whatever swimming pool coatings are made of, which is clearly the hardest material in the universe.

  4. myob
    Boffin

    Watch cover glass

    Sapphire has been used as the cover glass on watches for a long time (at least on the high end). It is also used for infrared optics that require a certain amount of robustness.

  5. Andrew Moore
    Coat

    But remember...

    I hope the manufacturers remember that trans-uranic heavy elements may not be used...

    1. Narlaquin
      Unhappy

      Re: But remember...

      Did you come here for a picture of Joanna Lumley too? I'm upset now.

      1. Anonymous Coward
        Happy

        Re: But remember...

        Oh yes. Those early "art" films featuring Ms Lumley that are no longer in circulation. Mmmmmmm.

    2. graeme leggett Silver badge

      Re: But remember...

      certainly not "where there is life"

  6. Spiracle

    Have a gorilla...

    Neddie: "Thank you."

    FX: 'Roaring and screaming'

    Neddie: "My, these gorillas are strong!"

    1. Andrew Moore

      Re: Have a gorilla...

      Neddle naddle noo!

      1. Ian Yates

        Re: Have a gorilla...

        Please... don't do that

    2. Sutekh
      Thumb Up

      Re: Have a gorilla...

      You silly twisted boy, you..

    3. I ain't Spartacus Gold badge
      Happy

      Re: Have a gorilla...

      I prefer a picture of Queen Victoria myself. Cork tipped, of course.

    4. Return To Sender
      Happy

      Re: Have a gorilla...

      Try one of my Monkeys, they're milder...

    5. Mayhem

      Re: Have a gorilla...

      No thanks ... I'm trying to give them up!

      1. Naughtyhorse

        Re: Have a gorilla...

        Sapristi!

        lot of goons in today!

        1. graeme leggett Silver badge

          Re: Have a gorilla...

          "lot of goons in today!"

          ...there's more where that came from...

    6. Armando 123

      Re: Have a gorilla...

      Moriarty ... I believe we found a Charlie ...

    7. Martin Budden Silver badge
      Childcatcher

      Re: Have a gorilla...

      He's fallen in the water!

  7. Craigness

    Fancy watches...

    ...use this, and some fancy Omega watches use liquid metal too, which Apple touted a while back. Those are also overpriced, but they're expected to last more than 2 years.

    Mean while, you can use a Lumia screen to drive a nail into wood.

    1. Darryl
      Coat

      Re: Those are also overpriced, but they're expected to last more than 2 years.

      Do you mean the watches or the Apple products?

  8. Anonymous Coward
    Anonymous Coward

    whyPhone

    Why specifically say the iPhone? There's nothing in this article to suggest that Apple are working on this, or are likely to be the first to use it.

    In fact, it's almost certain that the "next iPhone", due out this year will *not* have a sapphire screen - making the title of this otherwise good article doubly stupid.

    My guess is the writer of the article was not the writer of the idiotic linkbait headline.

    1. DaLo
      Meh

      Re: whyPhone

      Yeah, also wondering this. I thought when the author said " few chats with people who would know," I thought the Register had found someone with links to people at Apple.

      However the article doesn't mention that Apple are going to use this technology or looking at it.

      The author seems to have good knowledge of the industry and is providing a very factual and informative article but the whole premise of the article that the next iPhone could be using this undermines it. No evidence (even the "market analyst" quote is mentioned).

      1. Anonymous Coward
        Anonymous Coward

        Re: whyPhone

        Maybe because Apple tends to be on the cutting edge when it comes to materials and designs? okay, some of these designs are bling.

        But lets not forget that it was Jobs who introduced the phone market to Gorilla glass when he went looking for a cover for the iPhone 1's screen. Corning had discovered Gorilla glass many years ago and put it on the shelf.

        1. graeme leggett Silver badge

          Re: whyPhone

          some articles online say that Corning had invented a tough glass (Chemcor) in the 1960s which they stopped producing in the 1990s. Come the smartphone age, they started thinking what they could do, went back to Chemcor and came up with a new (and patentable) formulation which is Gorilla glass.

    2. Tom_

      Re: whyPhone

      Because the author was using "iPhone" as shorthand for "mobile phone at the expensive end of the spectrum where design is considered a significant factor in peoples' purchasing decisions".

      Take a step back and try to stop taking everything so literally. Language is able to convey more subtlety than that if you allow it.

      1. JDX Gold badge

        Re: whyPhone

        What Tom said - he means top end expensive phone.

    3. Bod

      Definitely not the first

      Vertu phones use sapphire glass for the screens. Along with stainless steel and titanium shells. Cough up more of those £1000s and you get precious metal bling and gemstones on top ;)

      1. GoingGoingGone

        Re: Definitely not the first

        And so did the more mundane (in comparison to Vertu) Nokia 8800 back in 2006. They even named it one of the variants "Sapphire Arte". If they had only announced it with a flamboyant presentation, patented it and reminded the world how they were 5 years ahead of anybody else...

        I'm getting myself a 8800 sirocco just to snottily pull it out of my pocket whenever a twat brandishes a shiny new gadget pontificating about its revolutionary sapphire screen and him being the first human being to ever hold one.

        Negative points for the author 'cos of the Apple baitlink + apparently not having a frigging clue that sapphire was used in phone screens even before the iPhone had seen the light of day.

    4. Anonymous Coward
      Anonymous Coward

      Re: whyPhone

      Well, Apple already use sapphire crystal for the camera lens in the iPhone.

  9. SW
    Joke

    Never mind the quality - feel the width !

    "elephant's tampon girth"

    Do I see a new candidate for inclusion in El Reg measurement standards?

    1. Phil O'Sophical Silver badge

      Re: Never mind the quality - feel the width !

      Hmm, it wasn't really the image I wanted to accompany my morning coffee, though.

      1. Naughtyhorse
        Thumb Up

        Re: Never mind the quality - feel the width !

        after you with the minds eye bleach!

      2. h4rm0ny

        Re: Never mind the quality - feel the width !

        "Hmm, it wasn't really the image I wanted to accompany my morning coffee, though."

        Think yourself lucky. I was eating raspberry yoghurt when I read that line. (I actually was).

      3. TeeCee Gold badge

        Re: Never mind the quality - feel the width !

        accompany my morning coffee

        Er, I don't think you're supposed to dunk them.

        1. Mephistro
          Coat

          Re: Never mind the quality - feel the width ! (@ TeeCee)

          "Er, I don't think you're supposed to dunk them."

          Unless you're a female elephant.

    2. Tim Worstal

      Re: Never mind the quality - feel the width !

      That is indeed my attempt to achieve lasting fame and reknown by having coined a neologism worthy of being included in the pantheon.

      1. Anonymous Coward
        Anonymous Coward

        Re: Never mind the quality - feel the width !

        There is no K in 'renown'.

  10. Harvey Trowell

    Ah yes, Hunting for Slags...

    Baden-Powell's somewhat less well received sequel to Scouting for Boys, wasn't it? Gave birth to the Girl Guides movement, something like that?

    1. Anonymous Coward
      Anonymous Coward

      Re: Ah yes, Hunting for Slags...

      I thought it was euphemism for a night out in Newcastle...

      1. Anonymous Coward
        Anonymous Coward

        Fixed

        Re: Ah yes, Hunting for Slags...

        I thought it was euphemism for a night out in any English town or city

        1. Anonymous Coward
          Anonymous Coward

          Re: Fixed

          > Hunting for Slags...

          OK, Google is not much help in this instance.

          I *presume* you are not a puritanical gunman looking to rid the world of women of "low repute".

          Could you give a clue to those of us that don't know what you're talking about?

          1. Martin Budden Silver badge

            Re: Fixed @ skelband

            Not hunting with guns, you silly person, merely "seeking out". You are, nevertheless, correct in your interpretation of the word slag.

            HTH

            1. Anonymous Coward
              Anonymous Coward

              Re: Fixed @ skelband

              I'm still a bit confused: what are the "slags" being hunted for in this instance?

              1. Ru

                Re: Fixed @ skelband

                I'm still a bit confused: what are the "slags" being hunted for in this instance?

                What might look like a common slag to the unitiated may in fact be a valuable ore, and worth a penny or two to the pimp prospector who stakes an appropriate claim and has a client in mind with suitably niche tastes.

    2. Anonymous Coward
      Anonymous Coward

      Re: Ah yes, Hunting for Slags...

      "My day job for the last year or so has been huntin' slags"

      - also an evening occupation of most blokes in Northern towns on a Friday and Saturday night

      1. JDX Gold badge

        Re: Ah yes, Hunting for Slags...

        In northern towns you don't exactly need to hunt for them, any more than you have to hunt for pools of sick.

      2. Anonymous Coward
        Anonymous Coward

        Re: Ah yes, Hunting for Slags...

        ""My day job for the last year or so has been huntin' slags"

        - also an evening occupation of most blokes in Northern towns on a Friday and Saturday night"

        As opposed to the southern towns, who do not need to go huntin' for them. They're at home.

    3. John L Ward

      Re: Ah yes, Hunting for Slags...

      "My day job for the last year or so has been huntin' slags in the famous Ore Mountains" - sounds even funnier if you say it in a pirate voice...

      1. Mayhem

        Re: Ah yes, Hunting for Slags...

        Oh aye, oop north has always been famous for its ores.

        Nowadays of course it's mostly slags you're finding.

  11. Voland's right hand Silver badge
    Devil

    Fantastic

    We shall all congratulate Apple with innovating this new and wonderful innovation in the world of consumer electronics. This is so exciting and such a good reason to buy this new and innovative gadget. I just cannot wait until the hype wave starts rising and all the usual suspects try to ride it under the rainbow and into the sunset.

    They will call fossilized grumpy old men those of us who can remember that Motorola KRZR K1 (2006) shipped with a Al203 glass (and you could use it as a hammer or chisel - best built phone I ever seen, pity the software was major s***age). Actually my Poljot high school watch from 30 years ago used it and so does my current Fossil.

    It is the usual Apple - taking an old, tried, tested tech, twisting the arm of a few manufacturers to mass-produce it and doing the mother of all marketing campaigns to pretend to have innovated it.

    1. Andrew James

      Re: Fantastic

      The article doesn't mention anything about Apple using the tech. The headline is clickbait and nothing more. So calm down.

      1. Anonymous Coward
        Anonymous Coward

        Re: Fantastic

        Nothing personal Mr. James, but don't most of us read most of the articles here, anyway? Or is it just me?

        1. Andrew James

          Re: Fantastic

          Most of the regulars probably read most of the articles, but headlines like this will lure in traffic from elsewhere, and cause anti Apple nutcases to froth at the mouth before they get chance to reach the opening paragraph.

  12. LesB
    Thumb Up

    I saw what you did there...

    Sapphire and steal, eh? Nicely done.

    1. Imsimil Berati-Lahn
      Go

      Re: I saw what you did there... All I have to say on the matter is...

      All irregularities will be handled by the forces controlling each dimension.

      Trans-uranic heavy elements may not be used where there is life.

      Medium atomic weights are available.

      Gold, lead, copper, jet, diamond, radium, sapphire, silver and steel.

      Sapphire and steel have been assigned.

  13. Mystic Megabyte
    Boffin

    U+1F716

    If I could be bothered to switch off my Adblocker I'm sure that this page is full of ads for...

    "Sea monkeys - watch them swim!"

    "Grow your own crystal garden"

    "X-Ray Specs!"

    etc.

  14. Zola
    Go

    Given the rectangular shape of phones

    and the circular shape of ingots, that's going to mean an absolute boat load of wastage while they make a round ingot fit a rectangular hole. Maybe the offcuts can be sold on to the watch industry...

    1. I ain't Spartacus Gold badge

      Re: Given the rectangular shape of phones

      Don't be silly. The next iPhone will simply be round. Problem solved, and ground prepared for next Samsung lawsuit. And of course, the most rounded corners of any square ever made...

  15. Adrian Harvey
    Go

    Sapphire glass is already in use on the iPhone

    Only to cover the camera lens on the iPhone 5 though. But perhaps it shows intent...

    1. Anonymous Coward
      Go

      Re: Sapphire glass is already in use on the iPhone

      I agree the fact Apple already uses sapphire in the iPhone 5 makes it more likely that Apple uses it for the screen than anyone else. On the other hand Apple has a deal with the maker of Liquid Metal giving them an exclusive license in the field of consumer devices and used it for the SIM tool a couple phones ago....and nothing since.

      Just because they used it for the camera lens doesn't mean they'll find it practical to use it for the screen. Remember the complaints about the purple tint in photos showing up at certain angles? Yep, the sapphire's responsible. Apple is big on very accurate color reproduction on their displays, they would have to find a way around this before they'd consider using it for their display glass.

      It would be interesting if they went to a Liquid Metal body and sapphire screen. The entire phone would be essentially scratchproof, though the screen itself would likely be not all that much different in shatter resistance than glass, nor would the body be wildly less susceptible to dents than the aluminum used in the iPhone 5. There is unfortunately typically a relationship between the hardness of a material and its resistance to shattering. If you want something to not shatter, you want it to be flexible, not stiff. Flexible things typically will either dent or scratch depending on the type of flexibility. If they're flexible but spring back then they're the kind of thing more likely to shatter due to fatigue. Kind of a vicious material circle.

      Scratchproof, shatterproof AND dent proof? Not going to happen. There will never be a perfect material for cell phone screens or bodies that is both resistant to scratches from typical use (pockets, purses and the things normally kept within) as well as able to survive a drop from ear height onto concrete without scratches or dents from all likely impact angles. Well, shouldn't say never, nanotechnology may save the day, but we haven't found anything yet that can do this, even at the "crazy rich guy" end of the spectrum, let alone the "we can build it for $200-ish and sell it for $600-ish" range that iPhone and Samsung Galaxy S* play in.

  16. Anonymous Coward
    Anonymous Coward

    Star Trekkin'

    "Aluminium is, of course, a metal, while sapphire is an aluminium oxide: it's not quite and wholly true to say that it's just aluminium glass but it's a useful way of thinking about it."

    Aye captain, transparent aluminium...

    ;-D

  17. Arachnoid
    Facepalm

    Its not a rectangle its a long sided square with round corners as per the patent.....

    My I hope your misses understands the inference of what your hunting for but its good to know manufacturers are pandering more to the careless end user who treat tech as throw away items.

  18. Portent
    Thumb Up

    Where's Silver?

    I'm loving the Sapphire and Steel reference :)

    1. Anonymous Coward
      Anonymous Coward

      Re: Where's Silver?

      You're the 2nd or 3rd person to mention this, I guess I'm going to have to refer to Google to see what this is about.

  19. Anonymous Coward
    Anonymous Coward

    Sizes?

    "Currently, at least with the pieces I've seen, it's about the shape and size of the sort of candle you might put on a dinner table. "

    Yet,

    "a material that’s used as transparent armor[sic] on military vehicles"

    hmm.. something doesn't seem right there...

    1. Phil O'Sophical Silver badge

      Re: Sizes?

      One is a drawn ingot, the other is a deposited coating.

      Although a Humvee decorated with candles would certainly give one pause for thought.

      1. Paul Crawford Silver badge

        Re: Sizes?

        Not as much as a Humvee decorated with elephant tampons!

    2. Ru

      Re: Sizes?

      There's at least one company who can make transparent alumina slabs which aren't fancy single-crystal ingots. They're not quite as resilient as the higher-quality offerings, but they're cheaper and already available in armoured vehicle window sizes.

  20. Chemist

    "Must try harder"

    Standard plain glass is silica (silicon dioxide)

    NO it isn't - it's a mix of sodium and calcium silicates + various other bibs and bobs

  21. cshore

    Glass?

    Surely it's completely wrong to describe it as "aluminium glass", or even to describe it as glass at all. Glass is an amorphous solid, sapphire is a crystal. "Glass" is just a handy word in this context for "substance which is hard and transparent."

  22. Michael H.F. Wilkinson Silver badge
    Boffin

    Silica <> glass

    Silica or quartz is not (often) a true glass. Fused silica is used in optics, but due to the high temperatures needed for glass transition it is limited in its use. Typical glass combines silica (about 75%) with sodium and calcium oxides. So silica is the main constituent in many cases, but not the whole story. Most silica typically has a proper crystalline structure, and is not glass-like in many properties (e.g. thermal conductivity of glass is typically closer to that of certain liquids than that of crystalline silica or carborundum (alumina)).

    </pedantry>

  23. Anonymous Coward
    Anonymous Coward

    Squares that look round

    I was assuming the ingot was a cylinder?

    Slice that through the vertical, then you have two square surfaces from which you can slice (admittedly smaller and smaller) square slivers/slice

    In the short term (low yield) the diameter of the ingot only needs to be a little bigger than the width of the screen you want to make, by a little longer. Lots of wastage, but probably do able with the current "fat candle" ingots.

  24. Dazed and Confused

    I don't know what size candles you use for Slag bait but

    When I used to work in chip research we were baking them on 3" diameter wafers of Sapphire back in the early 80s. SOS had some significant advantages if you're concerned with making stuff rad hard, silicon is for softies who live on the ground.

    I thought the production side of the business was using bigger wafers even back then.

    Typing Silicon on Sapphire into Google shows an ad at the top for 300mm wafers! So they could already make iPod/any chosen brand of fondle slab screens if anyone cared enough to try.

    I remember finding a whole load of old 2" wafers in the back of an old cupboard and one of the managers taking them with the intention of making the world most bling lamp shade.

  25. reno79

    I know it's not the bastion of reporting that El Reg is but CNet did a similar report a while back mainly concentrating on the applied tech rather than the research behind it.

    http://cnettv.cnet.com/virtually-indestructible-sapphire-smartphone-screen/9742-1_53-50141889.html

  26. Anonymous Coward
    Anonymous Coward

    Looks like they've achieved 6" dia. sapphire ingots now

    http://d27vj430nutdmd.cloudfront.net/18411/102964/102964-14.pdf

  27. John Savard

    Birefringent

    It's a pity that sapphire's birefringent. It has a high refractive index, but low dispersion, so it would otherwise be an ideal material for lenses.

    1. This post has been deleted by its author

  28. Anonymous Coward
    Thumb Up

    I henceforth refuse to read any technology publication which lacks a dedicated mining correspondent.

    1. Tim Worstal

      That would be good

      Given that I'm just about the only freelance around who both knows his mining stuff about weird metals and also has even a passing knowledge of tech......lots more commissions then!

  29. Martin Budden Silver badge
    Joke

    Why do elephants have trunks?

    Because sheep don't have string.

  30. markm398

    Old news! Sapphire is already used on Android

    On the ridiculously expensive Vertu Ti. Stupendously expensive, but someone mus have cracked (no pun intended!) the technology of making large area sapphire...

  31. John Savard

    Lanthanum oxide

    Lanthanum oxide doesn't make glass more transparent. But it does allow the production of glasses with high refractive index and low dispersion, which are desirable characteristics for designing lenses which produce good images (the lens doesn't split the colors as much, so it doesn't need as thick a flint correcting element, and the lens doesn't need to be as thick itself to bend the light for a given focal length). High-quality astronomical eyepieces, therefore, often use elements which contain that material.

  32. cray74

    Artificial sapphire

    Sapphire watch faces are an old technology, grown by flame deposition (Verneuil process, 1902AD) or by growing a boule from a tub of molten aluminum oxide (Czochralski process, 1916). The latter can produce bars of aluminum oxide up to 400mm diameter and is a workhorse of the watch industry, which has been using sapphire watch faces for decades. Replacement sapphire watch faces can be as cheap as $15 (US).

    While sapphire is a fantastically hard material, and thus more scratch resistant than Gorilla glass, it is not particularly tough (crack resistant). It is a poor man's ceramic armor, displaced by silicon carbide, silicon nitride, and boron nitride in (opaque) armor applications.

    On the other hand, Gorilla glass's virtue is its toughness (by transparent glass / ceramic standards), which suits it for thin, lightweight phone screens. If you use an equally thin sheet of sapphire in your phone, I'm betting it'll crack more often even while resisting scratches. (And if you try to drive nails with a sapphire phone screen then you're going to have a nail embedded in your phone before long. )

    I've liked the idea of sapphire for phone screens for a while because of its history in watches. But phones use thinner, larger sheets than a robust Rolex "crystal" in a thick, small watch case. There'll be more bending and torque than in a watch.

    So, I plan to sit out the sapphire phone screen race until a few more generations have come and gone and engineers have ironed out the vulnerabilities.

    And a nitpick: sapphire, aluminum oxide, is not "transparent aluminium" (or "solid oxygen") anymore than water is "liquid hydrogen." Aluminium oxide is a chemical compound with completely different properties than its base elements. Different melting point, different strength, different hardness, different chemical behavior, etc.

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