Yunyi Wu

Liquid metal soft electrode triggered discharge plasma in aqueous solution

This paper reports a fundamental phenomenon whereby discharge plasma can be easily triggered in aqueous solution under a low voltage via a liquid metal electrode that is either static or a jetting stream. Plasmas with light emission are generated, which could last for several milliseconds each time, yet with a consistent current. The principal peaks of such optical emission spectrum lie in the blue, violet and ultraviolet sections, which are mainly caused by the plasma of gallium and indium. The influence of condition changes, such as voltage direction and solution constituents, on this phenomenon was also investigated. Further, this method to produce plasma has also been demonstrated to be useful for the fabrication of micro-sized metal particles or other compounds.

Thickness- and temperature-dependent structural and electromechanical properties of (100)-oriented Sc-doped (Na0.85K0.15)0.5Bi0.5TiO3 ferroelectric films

(100)-oriented Sc-doped (Na0.85K0.15)0.5Bi0.5TiO3 (NKBT-Sc) films with different thicknesses of about 100–620 nm were grown on Pt(111)/Ti/SiO2/Si substrates by a sol–gel method. A LaNiO3 (LNO) layer of about 20 nm thickness was introduced at the film–substrate interface or alternatively with NKBT-Sc layers to form a sandwich multilayer structured film. The film thickness- and temperature-dependent structural and electromechanical properties of the films were investigated. A rhombohedral–tetragonal phase transition phase occurred with the variation of NKBT-Sc film thickness, and during this process a two-phase coexistence existed in an appropriate film thickness region, inducing an increased remnant polarization (Pr) value at an intermediate thickness (∼460 nm) of about 23.7 μC cm−2. The effective piezoelectric coefficient initially increased from about 32 pm V−1 for the thinnest film (∼100 nm) to a peak value of about 73 pm V−1 (∼460 nm), but then decreased as the film thickness further increased. With the insertion of the LNO layers alternatively inside the NKBT-Sc film, the sandwich multilayer structure further enhanced the degree of the (001)-orientation and was beneficial for the crystallization process, leading to better electromechanical properties than the NKBT-Sc/LNO/substrate structure composite film. A high piezoelectric coefficient of about 82 pm V−1, dielectric constant er of about 523 and remnant polarization (Pr) of about 26.2 μC cm−2, which gradually increased with the decrease of the testing temperature from 20 °C to −120 °C, together with a with a low dielectric loss (tan δ) of about 0.055 were simultaneously obtained in the sandwich multilayer structured film with NKBT-Sc film thickness of about 460 nm.