Abstract
By the use of a ring type electrode made of platinum,the electrical conductivities of PbO-SiO2 binary melts ranging in composition 30 to 64 mol%SiO2 have been measured over the temperature range 800° to 1200°C. Liquid structure and structural change of lead silicate have also been estimated from the present results and the data of density, viscosity and surface tension reported in the previous papers. The results obtained are summarized as follows:
(1) The specific conductance obeys the Rasch-Hinrichsen equation, κ=Aexp(−E⁄RT), in the range of composition 35 to 50 mol%SiO2. However, in the ranges of more or less than that composition, the specific conductance shows a possitive or negative deviation from the straight line. It may probably be due to the formation of polyhedra consisting of ring type anions and Pb2+ ions and homopolar Pb-O bonds.
(2) The specific and the equivalent conductances decrease with increasing content of SiO2 and show characteristic inflections around the stoichiometric compositions of 2PbO·SiO2 and PbO·SiO2. It may indicate the structural change in these compositions by the network-breaking effect of lead oxide.
(3) The heat of activation for conductance increases with increasing content of SiO2 and shows a characteristic plateau in the range of composition 38 to 45 mol%SiO2.
(4) The heat of activation for viscous flow is smaller than that for equivalent conductance in the range of composition less than 55 mol%SiO2. It is considered that the major controlling factor for the activation mechanism changes arround this composition.
