Optical emission laser microprobe analysis of synthetic oxide monocrystals

Abstract

The existing methods of laser microprobe spectrochemical analysis are reviewed. Some atomic emission spectroscopic (AES) methods analysis for synthetic high-melting oxide monocrystals applying solid lasers have been studied by the authors. A two-stage method of analysis of monocrystals including preliminary laser sampling with condensation of the ejected substance on the plane surface of a graphite rod and subsequent AES analysis of the condensate in an independent excitation source was developed and used. The method proved to be more efficient than other laser analysis methods studied. The regularities of laser ejection of Ca 2V 2O 7 monocrystal substance, the composition and distribution of its condensate on the surface of a substrate serving as a collector of the condensate were investigated in model experiments. The identity of the elemental compositions of condensate and the monocrystal analysed was shown. Dry residues of standard aqueous solutions served as reference samples. A unipolar impulse discharge and an a.c. arc were used as the excitation sources for the condensate spectrum; the a.c. arc turned out to be more suitable. The correctness of the quantitative determination of the impurities doped in Ca 2V 2O 7 monocrystals when applying the two-stage laser microprobe analysis was proved by the direct AES method of analysis of the same monocrystals which had been completely dissolved. Examples of practical application of the two-stage laser analysis method for the investigation of calcium vanadate monocrystals and also examples of the direct d.c. arc AES analysis method for the investigation of synthetic monocrystals of titanium dioxide are given.