CORRELATION BETWEEN THE STRUCTURE AND MECHANISM OF ELECTRIC CONDUCTIVITY OF SOLID MgHPO//4 multiplied by (times) 3H//2O

Abstract

Electric and thermal properties of solid MgHPO//4 multiplied by (times) 3H//2O have been investigated in the temperature interval 293-673 K and correlated with data obtained during crystallographic analysis. Within the temperature interval 293-463, a sample is characterized by a slight conductivity in spite of the presence of considerable hydrogen. The sample loses the crystal water within the temperature interval 463-473 K thus causing formation of the acid salt MgHPO//4. The enthalpy of this endothermal process is equal to 2. 88 kJ/g. The structure of the dehydrated salt is similar to that characterizing other acid phosphates and shows a better conductivity. In this case the proton conductivity with an activation energy of 42. 12 kJ/mol occurs by tunneling of protons along hydrogen bonds and followed by rotation of phosphate groups.