MEASUREMENT OF THE SHEAR VISCOSITY IN GARNET HIGH-TEMPERATURE SOLUTIONS BY A CYLINDRICAL ROTATION VISCOMETER

Garnet high temperature solutions, their solvents and binary systems consisting of lead oxide and one component out of the solute were investigated. The shear viscosity coefficients have been measured in a cylindrical rotation viscometer within the temperature range of liquidus or melting and not exceeding 1270°C. The logarithm of the shear viscosity in the simple systems PbO or PbOB2O3 linearily depends on the reciprocal absolute temperature, however, the relationship in phase systems containing Fe2O3 or Ga2O3 is more complex. The shear viscosities of Y3Fe5O12 or (Y, Sm)3 (Fe, Ga)5O12 solutions suitable for LPE experiments amount 0.20 to 0.23 g cm−1s−1 near the liquidus temperatures. An effective average activation energy for shearing flow was estimated, its dependence on the temperature points to chemical equilibria reactions in the solutions. Copyright © 1979 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim