✍ Scribed by Armin Wyttenbach; H.E. Blum; W.J. Borer; H.K. Eigenmann; Hs.H. Günthard
No coin nor oath required. For personal study only.
Impurities in the p.p.m, range in sapphire and ruby single crystals have a considerable influence on the optical and magnetic properties of these materials. Unfortunately, the determination of dopants such as Ti, Cr, Mn, and Fe in corundum single crystals in small concentrations poses some problems.
Destructive analyses by fusion of the finely powdered crystal material with borax-alkali hydroxide at 1000 ° or pyrosulfate fluxes at 400 ° suffer seriously from the introduction of impurities through the reagents and, as has been shown by Dodson 1, from the uncontrolled exchange of certain impurities between melt and crucible. Nevertheless, chromium 1'2 and cobalt 3 have been determined by wet analysis and colorimetric methods. The problems of impurities and interferences are largely eliminated by the hydrofluoric acid bomb technique 4, but local and nondestructive investigations are not feasible by this method. Atomic absorption spectroscopy should offer some advantage in this type of trace analysis; however, it too suffers from the restriction with regard to the purity of the chemicals used for fusion, Future development of hollow-cathode emission tubes not requiring liquid samples might circumvent these drawbacks. The use of a laser microprobe for emission spectral analysis has been attempted for a number of trace elements in ~-A120 3 in this laboratory, but it was found difficult to obtain sufficient reproducibility.
In this paper are reported the results of an investigation of trace analysis by instrumental neutron activation (i.n.a.a.) and electron microprobe (e.m.p.) for titanium, chromium, manganese and iron in doped sapphire single crystals in the concentration range up to 700 p.p.m. The effort is concentrated on the establishment of a significant correlation between the two methods and on detectability ranges. Besides Ti, Cr, Mn and Fe, many other trace elements have been determined in ~-A 1 2 0 3 single crystals by both techniques, but no attempt has been made to establish correlations similar to those reported here. These correlations might serve as an appraisal of the use of the electron microprobe and instrumental neutron activation analysis for the determination of elements for which no calibration standard is readily available. Very probably these techniques can be applied also to other single crystals for nondestructive trace determination and therefore appear to have a wide use.
📜 SIMILAR VOLUMES