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American Association for Crystal Growth — AACG |
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Through a combination of donations, gifts, and the loan of single-crystals, the AACG collection of crystal-growth specimens has grown from a small set of single-crystal samples to what may well be the world's largest and most varied collection of man-made crystals. If the collection does not currently satisfy this criterion, it is certainly well on its way to meeting such a goal since new crystals are being added at a steady rate through the generosity of both crystal-growth companies and individual donors. The collection provides a showcase for examples of single crystals that are grown by a variety of techniques, and it illustrates seeding phenomena as well as the dependence of crystal morphology on the growth method. Included in the collection are single crystals of metals, semiconductors, and insulators – the latter category being primarily represented by a wide variety of oxide specimens plus a number of halides.
Composite shot of overall view of both cases The genesis of the efforts to create a formal collection of crystal-growth specimens can be traced to a request made by Brian Maple, a physics professor at the University of California – San Diego. Maple was responsible for organizing a number of displays for the Centennial Meeting of the American Physical Society (APS), and he thought that a display of single-crystal research materials would be particularly appropriate for the Centennial APS meeting that was to be held in Atlanta, GA in March of 1999. This March meeting is the traditional bastion of condensed matter physics, and the APS went all out to make the 100-year anniversary a very special and successful event. Brian Maple had previously seen what was a modest, informal collection of man-made single crystals during his visits
to Oak Ridge National Laboratory (ORNL). This small collection consisted of samples that had been grown in conjunction with ORNL research activities over a number of years plus a few specimens obtained by “bartering” ORNL-grown material for other crystals grown elsewhere – a practice that is not uncommon among crystal growers. As modest as the ORNL collection was, Maple felt that it would be appropriate for the Centennial APS March Meeting, and contact was made in order to arrange for presenting the display in Atlanta. When the actual preparations for organizing the APS March Meeting display were underway, it quickly became evident that additional samples were going to be needed or the exhibit was going to look pretty sparse. The collection was in definite need of some serious “beefing up.” In a stroke of good fortune, Bill Bonner, a past AACG President and the founder and owner of Crystallod, Inc., called on an unrelated matter about that time, but before he could escape, he had been convinced to loan a variety of single crystals for inclusion in the Atlanta exhibit. With the addition of the samples from Crystallod, and with the help of Brian Sales, an ORNL research scientist, it was possible to present a respectable display of man-made research materials and single crystals at the Centennial APS meeting.
In an incident that is more amusing in retrospect that it was at the time, what has now become the AACG Crystal Growth Collection was almost lost before it could really get started in earnest. People who had display materials in a very large exhibit hall at the Convention Center in Atlanta had been told to remove their material by 3:00 pm on the last day of the APS meeting. About 10:00 o'clock that morning, however, I began to get a “not good” feeling about the crystal exhibit and decided not to wait until the afternoon to remove the material. When I arrive at the exhibit hall about 10:30, all hell had broken loose. About a hundred men (I would call them the “bull gang.”) were swarming everywhere, and forklifts, and carts were being driven at suicidal speed with little or no regard for human life or safety. Large girders loaded with clusters of lights were descending rapidly and at random, and the walls of exhibit booths were crashing down all around. I couldn't find the glass display case that housed the crystals anywhere in this total chaos, and a thin veneer of sweat (that subsequently became a river of sweat) began to form on my face. I finally located the display case where a forklift had deposited it behind a pile of dismantled booths. The crystals were all there – in one large mound. Fortunately, Bryan Chakoumakos, an ORNL crystallographer who was also looking for some lost display items, came along at that time, and with his help and by working like mad (while trying to stay alive) we managed to wrap and pack and save all of the single-crystal specimens. In the finale' to this activity, while carrying a large box filled with carefully wrapped crystals to my car and away from the ongoing carnage, I slipped in a torrential downpour and fell very hard right into the middle of an extremely large puddle of water and mud. Even though I fell forward, I wound up on my back in the water - but holding the box of crystals up at arm's length and out of harm's way. This was accomplished much to the amusement and delight of a passing group of teenagers. It clearly made their day, and it was so ludicrous that I couldn't do anything but sit in the puddle and laugh along with them.
Near the conclusion of the exhibit in Atlanta, Judy Franz, the APS Executive Director, expressed an interest in having the single crystals on display at the APS and American Institute of Physics (AIP) headquarters building in College Park, MD. Subsequently, I used the occasion of attending a committee meeting at the APS/AIP headquarters as an opportunity to examine the two built-in display cases where the single crystal display would reside. Each of the cases was a foot deep and about fifty inches square – really too large for the single-crystal collection as displayed in Atlanta. Scientists ranging all the way from high-energy physicists to biophysicists were going to see a display at the APS/AIP headquarters, so this kind of opportunity for showcasing the science and art of crystal growth was clearly worth expending additional effort to expand the collection to fit the display cases. Specimens provided by Bill Bonner at Crystallod were already in the exhibit, but a number of other crystal-growth companies really “stepped up” and were willing to provide display specimens either on loan or as a donation for the APS/AIP exhibit. Accordingly, the new display in College Park, MD included a very large single crystal of hydrothermally grown quartz provided by Gary Johnson of Sawyer Research Products and a number of both as-grown and faceted emerald, sapphire, and ruby crystals provided by Tom Chatham of Chatham Created Gems. Gabe Loiacono of Coherent Crystal Associates came through with a large crystal of solution-grown nickel sulfate hexahydrate a well as a specimen of flux-grown potassium titanyl arsenate, and Joe Wenckus arranged for the donation of a large uncut single crystal of skull-melt-grown cubic zirconia from Ceres Corp. The display at the APS/AIP headquarters was in place for one year (from June of 2000 to June of 2001). It had been very well received and the subject of many favorable comments and the staff was reluctant to see it go.
One aside, again amusing only in retrospect, relates to the crystals from Chatham Created Gems, and it should be mentioned. When the box containing these specimens arrived from Chatham, I began to blithely unpack it and randomly put the crystals around here and there on the top of my desk. When, at the bottom, of the box I found the packing list/invoice and the associated valuation for the samples, however, my mood took on a more somber and serious tone. I immediately began to systematically inventory each and every crystal and to carefully mark it off against the packing list. The only problem was that at the end of this operation, there was one, quite valuable, crystal that was not accounted for. A thin veneer of sweat (that subsequently became a river of sweat) began to form on my face. I looked under my desk, under the mat, on the floor, through the packing material – everywhere. I enlisted the help of colleagues, crawled all over the floor of my office multiple times, but the crystal was not to be found. Finally, I was ready to call Tom Chatham and tell him that the crystal was missing and that either they had never sent it or I had simply lost it somewhere in my office. Just before I was ready to dial his number, I spotted a small piece of bubble wrap that was taped to a metal caliper-type crystal holder. When I removed the tape and unrolled the bubble wrap, out came the missing crystal. I immediately had everything locked up in the safe where we keep our platinum crucibles and left for the day. The next stop for the exhibit was to be the American Museum of Science and Energy (AMSE) in Oak Ridge, TN. The museum is supported currently by the U.S. Department of Energy. With about 25,000 visitors per year, it also serves as an educational resource for K-12 students throughout the region. AMSE lacked built-in display cases like those found at the previous APS/AIP site in College Park, MD, so special Plexiglass cases were designed by Jim Kolopus, an ORNL crystal growth and fabrication technician, and then built to house the crystals. We decided to use hexagonal cases, and these were constructed beautifully by Rex Hahn, a museum display staff member. Joanne Ramey and Allison Baldwin of ORNL did an outstanding job of creating new clear legible labels and signage that identified the crystals, the growth method, and that gave credit to the donors of the specimens. Additionally, through the outstanding efforts of Dave Brandle and Mike Digiuseppe, some very large, impressive, and beautiful garnet crystals were added to the collection about this time. The “enhanced”
single-crystal collection was then put on display at AMSE until July of 2002 when it was necessary to move it due to renovations that were to be done to the museum. At this point, the exhibit was moved to the Knoxville Regional Airport, McGhee Tyson Field where it currently resides. This is a high-profile location that is visited by 1.6 million people per year, and the two display cases with the crystals are located in a prominent position just past the security check point. The future of the American Museum of Science and Energy is presently not determined (It may become the “Manhatten Project Museum”), so it is not certain that the exhibit will (or should) return to AMSE from Tyson Field. If it does, plans call for the development of an educational module on the science of single crystal growth that would be appropriate for a K-12 audience. At the American Association for Crystal Growth (AACG) Executive Committee meeting that took place during the American Conference on Crystal Growth and Epitaxy in Burlington VT, the proposal was made to have the crystal growth collection become the “official collection” of the American Association for Crystal Growth. This proposal was approved unanimously by the AACG Executive Committee. Having the AACG assume “ownership” of and long-term responsibility for the collection is advantageous from the point of view of adding new specimens to the exhibit; since the AACG is a non-profit organization (both legally and in fact!), donations of crystals may be tax deductible. The display contains information about the AACG and even provides contact information. While we are not likely to generate many new AACG members this way, the display makes the public aware of the existence of the profession of crystal growth, what the output of this profession looks like, and what man-made single crystals can be used for. We still have a lot of work to do to improve the educational aspects of the exhibit, and we plan to work with some specialists in the educational field to further develop and improve this particular aspect of the display.
The most recent addition to the single crystal collection is an incredible single crystal of calcium fluoride that has been added through the initiative and efforts of Rick Schwerdtfeger, the Process Development Manager for Saint Gobain Crystals and Detectors, Solon, OH. A special black walnut stand was made for this large single-crystal specimen, and it was added to the display during a recent cleaning and maintenance of the exhibit at Tyson Field. In the design of the hexagonal Plexiglass display cases, we left plenty of room for the growth and expansion of the AACG Crystal Growth Collection. New display-quality single crystals are very welcome and are solicited. Specifically, it would be nice to have a polished 12-inch-diameter segment of a silicon single crystal. The Si single crystal that is currently in the collection is a 4-inch-diameter Czochralski-grown boule that is hardly representative of the current state-of-the-art. A polished piece of one of the giant sapphire crystals that are grown these days would be great to have as well. Anyone who is interested in adding a specimen or specimens to the AACG Crystal Growth Collection should feel free to contact:
Posted by Gopal Rao, Web Science Editor, MRS
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