EFFECT OF HYDROGEN ON ELECTRICAL PROPERTIES OF RUTILE

Hydrogen in rutile has two influences on the electrical properties: Verneuil crystals contain hydrogen compensating the trivalent impurities. Excess hydrogen acts as an electron donor, thereby increasing the conductivity. Removal of hydrogen above 650°C in vacuum causes structural changes accompanied by enhanced conductivity and dielectric loss. There is also a change in the activation energy for diffusion at this temperature. Values of the coefficient of diffusion of protons in the temperature range 450-800°C in crystals of differing impurity content are presented. The position of the hydrogen, in the basal plane of the rutile lattice, is confirmed by the dichroism of the absorption. Weight-loss experiments suggest that hydrogen leaves the crystal in combination with oxygen in the proportions required to form water.