Effect of growth atmosphere on the tungsten monocrystals quality during zone melting

Effect of the controlled composition change in the residual atmosphere on the structure and purity of the tungsten monocrystals has been investigated. The tungsten monocrystals were grown by four zone runs with a single seed (its orientation is 10 deg from <110>) in a deep vacuum (1.34x10-6 Pa) and in a vacuum (6.68x10-3 Pa) with increased partial pressure of hydrogen. Composition change in the residual atmosphere in a melting chamber (increase of the hydrogen partial pressure) is shown to affect substantially the internal structure of specially pure tungsten monocrystals: the angle of disorientation between blocks decreases, dislocation density and relative residual electroresistance increase. The results of mass spectrometric analysis of the samples studied also show that contents of practically all analyzing impurities decreases during the controlled change in the residual atmosphere composition in the melting chamber