View source for Bridgman–Stockbarger method

{{short description|Method of crystallization}}
{{technical|date=March 2021}}
{{Crystallization}}The '''Bridgman–Stockbarger method''', or '''Bridgman–Stockbarger technique''', is named after physicist [[Percy Williams Bridgman]] (1882–1961) and physicist [[Donald C. Stockbarger]] (1895–1952). The method includes two similar but distinct techniques primarily used for growing [[boule (crystal)|boules]] (single-crystal ingots), but which can be used for solidifying [[polycrystalline]] ingots as well.

==Overview==
The methods involve heating polycrystalline material above its melting point and slowly cooling it from one end of its container, where a [[seed crystal]] is located. A single crystal of the same crystallographic orientation as the seed material is grown on the seed and is progressively formed along the length of the container. The process can be carried out in a horizontal or vertical orientation, and usually involves a rotating crucible/ampoule to stir the melt.<ref name="ScheelCapper2010">{{cite book|author1=Hans J. Scheel|author2=Peter Capper|author3=Peter Rudolph|title=Crystal Growth Technology: Semiconductors and Dielectrics|url=https://books.google.com/books?id=Jq9t9QE0LNwC&pg=PA177|date=25 October 2010|publisher=John Wiley & Sons|isbn=978-3-527-32593-1|pages=177–178}}</ref> The horizontal configuration can avoid placing stresses on the crystal due to thermal expansion and can purify the crystal at the cost of evaporation but the shape of the liquid-solid interface between the molten material and the crystal is more concave. Compared to the temperature gradient method where a temperature gradient is required along the entire length of the crucible, in vertical Bridgman method allows for a small temperature gradient only near the liquid-solid interface.<ref>https://books.google.com.pa/books?id=izaSIlOahJkC&pg=PA502&dq=heat+exchange+method+crystal+growth&hl=en&newbks=1&newbks_redir=0&source=gb_mobile_search&ovdme=1&sa=X&ved=2ahUKEwi59cb3k5qNAxUTQjABHeS7CtwQ6AF6BAgJEAM#v=onepage&q=heat%20exchange%20method%20crystal%20growth&f=false</ref>

The Bridgman method is a popular way of producing certain [[semiconductor]] crystals such as [[gallium arsenide]], for which the [[Czochralski method]] is more difficult. The process can reliably produce single-crystal ingots, but does not necessarily result in uniform properties through the crystal.<ref name="ScheelCapper2010" />

[[File:Bridgman-Stockbarger-Technique.svg|400px|thumb|Diagram of the Bridgman-Stockbarger method]]

The difference between the Bridgman<ref>{{cite journal|last1=Bridgman|first1=Percy W.|title=Certain Physical Properties of Single Crystals of Tungsten, Antimony, Bismuth, Tellurium, Cadmium, Zinc, and Tin|journal=Proceedings of the American Academy of Arts and Sciences|date=1925|volume=60|issue=6|pages=305–383|doi=10.2307/25130058|jstor=25130058}}</ref> technique and Stockbarger<ref>{{cite journal|last1=Stockbarger|first1=Donald C.|title=The Production of Large Single Crystals of Lithium Fluoride|journal=Review of Scientific Instruments|date=1936|volume=7|issue=3|pages=133–136|doi=10.1063/1.1752094|bibcode = 1936RScI....7..133S }}</ref> technique is subtle: While both methods utilize a temperature gradient and a moving crucible, the Bridgman technique utilizes the relatively uncontrolled gradient produced at the exit of the furnace; the Stockbarger technique introduces a baffle, or shelf, separating two coupled furnaces with temperatures above and below the freezing point. Stockbarger's modification of the Bridgman technique allows for better control over the temperature gradient at the melt/crystal interface.

When seed crystals are not employed as described above, polycrystalline ingots can be produced from a feedstock consisting of rods, chunks, or any irregularly shaped pieces once they are melted and allowed to re-solidify. The resultant [[microstructures|microstructure]] of the ingots so obtained are characteristic of directionally solidified metals and alloys with their aligned grains.

=== Bagdasarov method ===
A variant of the technique known as the '''horizontal directional solidification method''' ('''HDSM''') developed by Khachik Bagdasarov ({{Langx|ru|Хачик Багдасаров}}) starting in the 1960s in the Soviet Union. It uses a flat-bottomed crucible made out of [[molybdenum]] with short sidewalls rather than an enclosed [[ampoule]], and has been used to grow various large oxide crystals including [[Yttrium aluminium garnet|Yb:YAG]] (a laser host crystal),<ref>{{cite journal|last1=Arzakantsyan|first1=M.|last2=Ananyan|first2=N.|last3=Gevorgyan|first3=V.|last4=Chanteloup|first4=J.-C.|title=Growth of large 90 mm diameter Yb:YAG single crystals with Bagdasarov method|journal=[[Optical Materials Express]]|date=2012|volume=2|issue=9|pages=1219–1225|doi=10.1364/OME.2.001219|bibcode=2012OMExp...2.1219A|doi-access=free}}</ref> and [[sapphire]] crystals 45&nbsp;cm wide and over 1 meter long.<ref>{{cite journal|last1=Montgomery|first1=Matthew|last2=Blockburger|first2=Clark|editor1-last=Zelinski|editor1-first=Brian J.|title=18 x 36 x 1.5 inch sapphire panels for visible and infrared windows|journal=Proc. SPIE|volume=10179 101790N-1|issue=Window and Dome Technologies and Materials XV|pages=101790N|doi=10.1117/12.2269465|series=Window and Dome Technologies and Materials XV|year=2017|bibcode=2017SPIE10179E..0NM|s2cid=125444288 }}</ref> However, the quality of the crystals grown by HDSM differ from the [[Czochralski method]], due to the problem of the problematic presence of bubbles.

==See also==
{{Portal|Manufacturing}}
* [[Float-zone silicon]]

==References==
{{Reflist}}

{{DEFAULTSORT:Bridgman-Stockbarger method}}
[[Category:Industrial processes]]
[[Category:Semiconductor growth]]
[[Category:Crystals]]
[[Category:Methods of crystal growth]]