High Concentration Sol-Gel Synthesis of BaHf0.05Ti0.95O3 to Prepare Ceramics with Significant Piezoelectric Properties

This paper deals with a new sol-gel route to synthesize $\mathrm{BaHf}_{\mathrm{x}} \mathrm{Ti}_{1-\mathrm{x}} \mathrm{O}_3(\mathrm{BHT})$ with x=0.05 in which some parameters (viscosity, colloids’ sizes…) of this highly concentrated sol are controlled by dilution in ethylene glycol to ensure a time stability for several months at room temperature. These stable BHT sols are then used to process by dip-coating thick films on $\mathrm{Si} / \mathbf{P t}$ substrates with a thickness around 50 micrometers. Moreover, densified bulk materials are obtained from these sols and their electromechanical characterization give a thickness coupling factor $\left(k_{\mathrm{t}}\right)$ of 47%. The first results show the strong potential of this lead-free piezoelectric material for applications in ultrasonic transduction and energy harvesting.