Dielectric, Ferroelectric, and Piezoelectric Performances of Poled Nb-Doped BZT-BCT Prototypes

This work is related to the study of a lead-free ferroelectric material and thus piezoelectric material. The barium zirconate titanate-barium calcium titanate (BZT-BCT) doped with ${2}\%$ of niobium is an alternative to the toxic lead zirconate titanate commonly known as PZT, which is the most used material in piezoelectric application; also it is a ferroelectric and thus a piezoelectric material. Nb-doped BZT-BCT piezoceramic thin films were grown by means of repeated chemical solution deposition routes (sol–gel method) over platinum coated silicon $700 \mu \text{m}$ -thick wafer. The chemical solution has been appositely prepared containing the stoichiometric amounts of metals to obtain the perovskitic structure of formula ${0}.{5}\text {BaZr}_{{0}.{19}} \text {Ti}_{{0}.{79}}\text {Nb}_{{0}.{02}}\text {O}_{{3}}-{0}.{5} \text {Ba}_{{0}.{7}}\text {Ca}_{{0}.{3}}\text {Ti}_{{0}.{98}}\text {Nb}_{{0}.{02}}\text {O}_{{3}}$ . A platinum electrode was sputtered through shadow mask and the wafer has been cut to obtain device prototypes made of niobium-doped BZT-BCT whose ferroelectric characteristics (PE loops) by varying the frequency and voltage have been studied on square capacitors of different areas. While cantilevers structures were used to assess the piezoelectric properties for pristine and poled state material by a laser vibrometer. In the case of the best stack, different poling processes were performed to find the best conditions which have led to an improvement in the ferroelectric behavior and an increase of the displacement of about four times.