Effect of Glycerol on the Growth Of BZT-BCT Thin Film Obtained by Sol-Gel Method

Barium Zirconate Titanate-Barium Calcium Titanate (BZT-BCT) is a promising piezoelectric material, whose properties make it a lead-free alternative to Lead Zirconate Titanate (PZT) to produce thin films for micro-electro-mechanical systems (MEMS). Among the possible techniques suitable to produce BZT-BCT thin films, sol-gel based processes appear particularly interesting because of their flexibility and cost-effectiveness. To obtain a thin layer of BZT-BCT via sol-gel deposition, a precursor solution must be prepared and spin-coated on a suitable support, that is subsequently heated to induce the evaporation of the solvents and the formation of a gel. A further thermal treatment at high temperature produces the crystallization of the desired phase. In this work, with the aim of obtaining thick, homogeneous BZT-BCT thin films, the effect of the presence of glycerol in the precursor solutions was investigated. To the purpose, a set of solutions was prepared with different amounts of glycerol. The solvents in each of the prepared sample were evaporated to assess the crystallinity of the residual gels. The gels were also calcined to evaluate the effect of glycerol on BZT-BCT in its bulk form. The solutions were then spin coated on supports and thermally treated, and the structural features of the obtained films were assessed by means of X-ray diffraction and profilometry. Results showed that glycerol was effective in inhibiting the crystallization of undesired phases from the solutions and promoted the formation of homogeneous films in the range of 168 up to 280 nm, depending on the glycerol content.