Progress Towards Piezoelectric (Ba,Ca)(Ti,Zr)O₃ Thin Film Using Wet Chemical Solution Deposition

Today, piezoelectric materials play an important role in numerous applications such as sensors, actuators, transducers, and energy harvesters. Piezoelectric energy harvesters cannot reach the efficiency and scale of solar cells or wind turbines, but they are excellent power sources where electrical cables are undesired and miniaturization is a key factor. Lead-based piezoelectric materials such as Pb(Zr,Ti)O₃ (PZT) is currently the most widely used material in such systems. This is due to their strong piezoelectric coefficient and electromechanical coupling coefficient. However, the use of PZT is not an option due to the presence of lead and<b> the development of alternative "greener" and "superior" materials</b> with comparable or better piezoelectric properties is required. Barium titanate (BaTiO₃) is one of <b>the suitable lead-free piezoelectric candidates</b> due to its promising piezoelectric properties. To improve its piezoelectric properties, several BaTiO₃-based solid solutions with different substituents have been studied. In 2009, some researchers have reported a significant breakthrough in BaTiO₃ perovskite doped with Ca and Zr atoms, leading to the (Ba,Ca)(Ti,Zr)O₃ (BCTZ) solid solution with an outstanding piezoelectric coefficient.<br/><br/>Since <b>BCTZ material offers promising piezoelectric properties</b>, making thin films of this material is of particular interest for use in various applications. Also, the integration of piezoelectric films on silicon (Si) or silicon nitride (SiN) based platforms is crucial for the miniaturization of electronic and photonic components. In this work, <b>wet chemical solution deposition (CSD) technique is introduced as a rapid integration</b> to develop a cost-effective, reproducible and high quality industrial pathway to piezoelectric BCTZ film on desired substrate. Therefore, the formulation of the environmentally friendly BCTZ precursor solution is highly important and must be stable prior to the CSD process with good wetting behavior and good homogeneity on desired substrate. Here we are able to develop<b> the environmentally benign BCTZ</b> inks based on the short carboxylic acid route as metal organic decomposition (MOD) method. These modified BCTZ inks can be deposited on several type of substrate such as LaAlO₃, SrTiO₃, Si, SiO2/Si and buffered Si using spin-coating or ink-jet printing techniques. After deposition, a comprehensive study of the thermal process is carried out to elucidate the nucleation and growth mechanism of the BCTZ film. This extensive study has led to<b> (<i>h</i>00) epitaxial BCTZ film with superior piezoelectric and ferroelectric properties on different substrates</b>. This approach presents some new specific challenges and opportunities to improve the functional and structural properties of epitaxial BCTZ films on different types of substrates prior to applications.<br/><br/>This newly developed approach will also simplify the cumbersome transfer of piezoelectric BCTZ film from single crystal substrate to flexible substrate, thus meeting the strict requirements for the<b> successful implementation of piezoelectric BXT material in several applications</b>.