Lithium lanthanum titanate ceramic as sensitive material for pH sensor: Influence of synthesis methods and powder grains size

The lithium lanthanum titanate (LLTO), prepared by two different methods (solid state reaction and sol–gel), has been studied as sensitive element for detecting the pH variations in aqueous solutions when used as a potentiometric sensor. This property is dependent on mechanical and thermal treatments of the synthesised powder. A screening design was performed with the material obtained by solid state reaction. Several parameters (grinding time, heating rate for sintering process…) have been optimized. The main step, which increases the sensitivity, is the grinding of the powder before a heat treatment when the LLTO is synthesised by solid state reaction. We suppose that a small grains size of the powder is favourable to the pH variations sensitivity. A comparison with LLTO synthesised by the sol–gel route without grinding is also shown. The sensitivities of these two materials to the pH variations are very similar.