Synthesis, characterization and proton transport properties of a mixed material—Zirconium titanium phosphate, a tetravalent bimetallic acid salt

Abstract

An advanced inorganic mixed material of the class of tetravalent bimetallic acid (TBMA) salt—zirconium titanium phosphate (ZTP) has been synthesized by sol–gel route. ZTP has been characterized for elemental analysis (zirconium, titanium and phosphorus by ICP-AES), spectral analysis (FTIR), thermal analysis (TGA), X-ray diffraction studies, SEM and surface acidity (NH 3 TPD method). Ion exchange capacity (IEC) of the material has been determined and the effect of calcination (373–773 K) on IEC studied. Chemical resistivity of the material has been assessed in various media—acids, bases and organic solvents. The protons present in the structural hydroxyl groups in ZTP indicate good potential to exhibit solid state proton conduction. The proton transport property of ZTP has been explored by measuring specific conductance at different temperatures in the range of 303–423 K at 10 K intervals, using Solartron Impedance Analyzer (SI 1260) over a frequency range 1 Hz to 32 MHz at a signal level below 1 V. Zirconium phosphate (ZP) and titanium phosphate (TP) have also been synthesized under identical conditions and characterized. Their proton transport properties have also been investigated for comparative studies. It is observed that, in all cases, conductivity decreases with increasing temperature. Conductivity performance of ZTP, ZP and TP is discussed based on conductivity data and activation energy. It is observed that ZTP exhibits enhanced conductance and the mechanism of transportation is proposed to be Grotthuss type.