Temperature dependence of dielectric relaxation in 12-tungstophosphoric acid hexahydrate at microwave frequencies

Abstract

Complex permittivity of 12-tungstophosphoric acid hexahydrate (H3PW12O40 6H(2)O), 6-WPA has been measured at microwave frequencies (X-band) in the temperature interval from 296 K to 350 K. From 296 K to 328 K 6-WPA displays dipolar relaxation of the Debye type at the frequency f(1)=9.30 GHz which corresponds to the relaxation time tau (1)=1.7x10(11) s. From 328 K to 350 K large changes of epsilon (f) and epsilon (f) take place. Two additional relaxations appear at frequencies f(2)=8.25 GHz and f(3)=10.80 GHz. These additional relaxations could be due to protonic entities that become excited at higher temperatures. An assignation of these relaxations to specific proton entities is proposed.