High pressure behaviour of KHSO4 studied by electrical impedance spectroscopy

Measurements of the electrical conductivity were performed in KHSO4 at pressures between 0.5 and 2.5 GPa and in the temperature range 120–350 °C by the use of the impedance spectroscopy. The temperatures of the α–β phase transition (TTr) and of the melting (Tm), determined from the Arrhenius plots ln(σT) vs. 1/T, increase with pressure up to 1.5 GPa having dT/dP∼+45 K/GPa. Above the pressure 1.5 GPa, the pressure dependencies of TTr and Tm are negative dT/dP∼−45 K/GPa. At pressures above 0.5 GPa, the reversible decomposition of KHSO4 into K3H(SO4)2+H2SO4 (and probably into K5H3(SO4)4+H2SO4) affects the electrical conductivity of KHSO4, with the typical values of the protonic electrical conductivity, c. 10−1 S/cm at 2.5 GPa.