Chemical analysis of ZnGeP2 as a new line of research of heterogeneity in bulk crystals

Chemical analysis coupled with the inductively coupled plasma atomic emission spectroscopy is proposed as a suitable method for determination of the phase heterogeneity of bulk ZnGeP2 crystals, which are excellent materials for non-linear infrared technique. The crystal phase heterogeneity is resulting from impurity phases ZnP2 or Ge, which are undetectable by traditional x-ray diffraction method because of their low content. The precise analytical procedure was developed using a well characterized homogeneous ZnGeP2 crystal as a standard reference material to analyze a series of bulk ZnGeP2 crystals with a low content of ZnP2 or Ge. In this case, all static (instrumental and methodical) errors of the analysis were corrected, and dispersion of the analytical results (random errors) for crystals tested was related to a spatial variation of the impurity phase content and its irregular distribution. The spread of the analytical results found for 15 independent weights of each test crystal is demonstrated graphically.