Synthesis, Characterization and Proton Transport Properties of Mixed Metal Phosphonate-Zirconium Titanium Hydroxy Ethylidene Diphosphonate

R. Thakkar and U. Chudasama*

Applied Chemistry Department, Faculty of Technology and Engineering, The M. S. University of Baroda, Vadodara-390 001, Gujarat, India

Novel hybrid material, zirconium titanium hydroxy ethylidene diphosphonate (ZTHEDP) of the class of tetravalent bimetallic acid (TBMA) salt was synthesized using sol-gel route. ZTHEDP was characterized for elemental analysis (zirconium, titanium and phosphorus by ICP-AES and carbon and hydrogen by CHN analyzer), spectral analysis (FTIR), thermal analysis (TGA), X-ray diffraction studies and SEM. Chemical resistivity of this material was assessed in various media-acids, bases and organic solvents. The protons present in the structural hydroxyl groups in ZTHEDP indicate good potential to exhibit solid state proton conduction. The proton transport property of ZTHEDP was 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-32 MHz at a signal level below 1 V. Zirconium hydroxy ethylidene diphosphonate (ZrHEDP) and titanium hydroxy ethylidene diphosphonate (TiHEDP) were also synthesized under identical conditions, characterized and their proton transport properties investigated for comparative studies. It is observed that, in all cases, conductivity decreases with increasing temperature. Conductivity performance of ZTHEDP, ZrHEDP and TiHEDP is discussed based on conductivity data and activation energy. It is observed that, ZTHEDP exhibits enhanced conductance and the mechanism of transportation is proposed to be Grotthuss type.

Keywords: Proton conduction, Tetravalent bimetallic acid salt, Zirconium titanium hydroxy ethylidene diphosphonate, Hybrid material, Mixed metal phosphonate