Studies Of The Effects Of Techniques On The Properties Of Bi_0.5(Na_1-xK_x)_0.5TiO₃ Lead-free Piezoelectric Ceramics

In order to study the effects of techniques on the properties of Bi_0.5(Na_1-xK_x)₀₅TiO₃ lead-free Piezoelectric ceramics, BNT-BKT lead-free piezoelectric ceramics were prepared by conventional mixed oxide techniques and Sol-Gel process respectively in this thesis.Six compositions of Bi_0.5(Na_1-xK_x)_0.5TiO₃ ceramics (abbreviated as BNKT100x) were prepared by conventional mixed oxide techniques. The effects of sintering temperature, polarizing conditions and compositions on the properties of the ceramics were systematically investigated. The properties of BNKT175 powders and ceramics synthesized by Sol-Gel process were investigated by means of modern analyses techniques. Relatively excellent technical parameters for preparing BNKT175 solution were obtained, and other compositions of BNKT ceramics were prepared in the same conditions.The main conclusions obtained from the works are as follows:1. From X-ray diffraction results, it was found that the morphotropic phase boundary (MPB) of Bi_0.5(Na_1-xK_x)_0.5TiO₃ exists in the range of X=0.15-0.20. The properties of BNKT175 ceramics sintered at 1180℃ for 2h are as follows: d₃₃=144, K_p=0.323, Q_m=135, ε_r=738, tan δ=0.031 respectively. It was found that the ceramics are relaxor ferroelectric from the pattens of dielectric constant vs temperature.