Synthetic Quartz with High Ultraviolet Transmission
`
`A. A. Ballman, D. M. Dodd, N. A. Kuebier, R. A. Laudise, D. L. Wood, and D. W. Rudd
`
`Quartz has been synthesized under hydrothermal conditions at rates of 1.78 mm/day in the presence of
`LlNO2 in Ag li11ed and Ag plated systems, and it is shown that such quartz has optical transmission
`between 1500 A and 3 p. equal, and in some cases superior to, natural quartz. The uv cutoff at about
`1500 A has been shown to be associated with Fe whose concentration may be reduced by procedures that
`reduce the concentration of charge compensating H+ in the lattice (growth in LiNO2) and by pro-
`cedures which reduce the concentration of Fe in solutions (inert conditions). Transmission near 3 p.
`is affected by OH which can be reduced by LiNO2.
`
`Introduction
`
`Experimental
`
`The optical absorption of synthetic quartz in the ir
`region has been studied considerably and it has been
`shown that OH is responsible for absorption in the 3-):
`region.‘—3 Recently, the optical absorption has been
`shown to correlate with acoustic absorption‘ and
`methods of hydrothermally growing quartz with low
`OH concentrations and high acoustic Q have been re-
`ported.“ It has been shown that quartz may be pre-
`pared from hydrothermal solutions in which the min-
`eralizer is NaOH and the growth rate is greater than
`1.78 mm/day with an OH concentration in the 15-30
`ppm range and a Q as high as 1 X 10‘, provided LiNO2
`is present in the growing solution.“ Mechanisms for
`the effect of LiNO2 on OH concentration and Q have
`been proposed.’ Vitreous silica and crystalline quartz
`with good ir, visible, and uv transmission are of great
`technological interest, and the transmission of low OH
`synthetic crystalline quartz, particularly in the uv, has
`not been reported. Earlier experiments have shown
`that deliberate iron doping markedly reduces the trans-
`mission in the optical range.3“° Large size inert
`(silver) systems capable of quartz growth in the absence
`of iron have recently become availab1e.“~”
`It now is
`possible,
`therefore,
`to investigate the properties of
`quartz grown in the absence of iron.
`‘We report here
`the results of a study of the optical transmission of
`quartz prepared under conditions known to exclude
`OH and of quartz prepared in the absence of Fe.
`
`The first five authors are with Bell Telephone Laboratories,
`Inc., Murray Hill, New Jersey 07974; D. W. Rudd is with
`Western Electric Company,
`Inc., Merrimack Valley Works,
`North Andover, Massachusetts.
`Received 29 February 1968.
`
`The conditions and equipment used in this work were
`those ordinarily employed in commercial quartz syn-
`thesis in NaOH solutions”»”:
`crystallization tem-
`perature—352°C;
`temperature difference (At) between
`crystallization and growth zones~44°C ; degree of fill——
`82%;
`pressure——1570 atm;
`solution—1 M NaOH
`(0.1 M Li+ salts where they were used); nutrient——fus-
`ing quality lascas—Brazilian crystalline quartz;
`seed
`orientation—basal plane, (0001); and rate—1.78 mm/
`day.
`Growth was conducted under three sorts of condi-
`tions.
`
`(1) Directly in a 4340 alloy steel autoclave. Such
`autoclaves have a protective layer of sodium iron
`silicate (acmite) that has been built up during previous
`runs, but the nutrient basket, baffle, seed frame, and
`seed holders are new low carbon steel in each run.
`In
`
`this paper, synthesis under these conditions is termed
`growth in an iron autoclave.
`(2) Conditions as in (1) except that the nutrient
`basket, baffle, seed frame, and seed holders are plated
`with 0.25 mm of Ag.
`In this paper, synthesis under
`these conditions is termed Ag plated.
`(3) Directly in a silver lined tube“ of the sort
`shown in Fig. 1. This tube is essentially a scaled up
`version of Kolb’s silver lined design.” The tube is sup-
`ported by a steel shell that is more than capable of sup-
`porting the pressure differences between the Water in
`the autoclave and the hydrothermal solution in the tube
`that take place during the run. The tube is closed
`with a Morey type” closure and silver sheet seal that
`makes it much more convenient to use than the welded
`closure tubes“ previously used for inert high pressure
`hydrothermal conditions. The percent of fill of water
`outside the tube was 83% for the conditions of our ex-
`periments, and this fill provided a satisfactory pressure
`balance. The seed, frame, baffle, seed holders, and
`
`July 1968 / Vol. 7, No. 7 / APPLIED OPTICS 1387
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