TiO 3 -Based Piezoelectric Materials

The lead-free piezoelectric ceramics display good piezoelectric properties which are comparable with Pb(Zr,Ti)O 3 (PZT) and these materials overcome the hazard to the environment and human health. The Bi 0.5 (Na,K) 0.5 TiO 3 (BNKT) is rapidly developed because of good piezoelectric, ferroelectric, and dielectric properties compared to PZT. The origin of giant strain of BNKT piezoelectric materials was found at morphotropic phase boundary due to crystal change from tetragonal to orthorhombic and/or precipitation of cubic phases, in addition to domain switching mechanism. The dopants or secondary phases with ABO 3 structure as solid solution are expected to change the crystal structure and create the vacancies which results in enhancement of the piezoelectric properties. In this work, we reviewed the current development of BNKT by dopants and secondary phase as solid solution. Our discussion will focus on role of dopants and secondary phase to piezoelectric properties of BNKT. This result will open the direction to control the properties of lead-free piezoelectric materials

Current Development in Lead-Free Bi

The lead-free piezoelectric ceramics display good piezoelectric properties which are comparable with Pb(Zr,Ti)O3 (PZT) and these materials overcome the hazard to the environment and human health. The Bi0.5(Na,K)0.5TiO3 (BNKT) is rapidly developed because of good piezoelectric, ferroelectric, and dielectric properties compared to PZT. The origin of giant strain of BNKT piezoelectric materials was found at morphotropic phase boundary due to crystal change from tetragonal to orthorhombic and/or precipitation of cubic phases, in addition to domain switching mechanism. The dopants or secondary phases with ABO3 structure as solid solution are expected to change the crystal structure and create the vacancies which results in enhancement of the piezoelectric properties. In this work, we reviewed the current development of BNKT by dopants and secondary phase as solid solution. Our discussion will focus on role of dopants and secondary phase to piezoelectric properties of BNKT. This result will open the direction to control the properties of lead-free piezoelectric materials

Microstructure and luminescence of VO2 (B) nanoparticle synthesis by hydrothermal method

This paper reports the way for the synthesis of nanoplate VO2 (B) particles with controlled morphology. Nanoplate VO2 (B) particle was synthesized by hydrothermal method. Microstructure of VO2 (B) particles were controlled by hydrothermal temperatures and use of Zn doping into VO2 (B) matrix. The microstructure of the particles was shifted from nanowires to nanoplate morphology by changing of hydrothermal temperatures. The doping of Zn into VO2 nanoparticles resulted in an effective achievement of VO2 (B) phase. In addition, luminescence of VO2 (B) nanoparticle was also controlled by the use Zn doping. These results suggest that the potential application of Zn doped VO2 (B) particles for potential application in optical and energy techniques

Effect of Surface Morphology and Dispersion Media on the Properties of PEDOT:PSS/n-Si Hybrid Solar Cell Containing Functionalized Graphene

We present the results on the effect of surface morphology and dispersion media on the properties of PEDOT:PSS/n-Si hybrid solar cell containing functionalized graphene (Gr). The hybrid solar cells based on SiNWs showed higher power conversion efficiency (PCE) compared to the planar based cells due to suppressing the carrier recombination and improving carrier transport efficiency. The PCE of hybrid solar cells could be improved by adding Gr into PEDOT:PSS. Different solvents including deionized (DI) water, ethylene glycol (EG), and isopropyl alcohol (IPA) were used as media for Gr dispersion. The best performance was obtained for the cell containing Gr dispersed in EG with a measured PCE of 7.33% and nearly 13% and 16% enhancement in comparison with the cells using Gr dispersed in IPA and DI water, respectively. The increase in PCE is attributed to improving the carrier-mobility, electrical conductivity, PEDOT crystallinity, and ordering

Thermoelectric Properties of Hot-Pressed Bi-Doped n-Type Polycrystalline SnSe

Abstract ᅟ We report on the successful preparation of Bi-doped n-type polycrystalline SnSe by hot-press method. We observed anisotropic transport properties due to the (h00) preferred orientation of grains along the pressing direction. The electrical conductivity perpendicular to the pressing direction is higher than that parallel to the pressing direction, 12.85 and 6.46 S cm−1 at 773 K for SnSe:Bi 8% sample, respectively, while thermal conductivity perpendicular to the pressing direction is higher than that parallel to the pressing direction, 0.81 and 0.60 W m−1 K−1 at 773 K for SnSe:Bi 8% sample, respectively. We observed a bipolar conducting mechanism in our samples leading to n- to p-type transition, whose transition temperature increases with Bi concentration. Our work addressed a possibility to dope polycrystalline SnSe by a hot-pressing process, which may be applied to module applications. Highlights 1. We have successfully achieved Bi-doped n-type polycrystalline SnSe by the hot-press method. 2. We observed anisotropic transport properties due to the [h00] preferred orientation of grains along pressing direction. 3. We observed a bipolar conducting mechanism in our samples leading to n- to p-type transition

Unidentified major p-type source in SnSe: Multivacancies

Tin selenide (SnSe) is considered a robust candidate for thermoelectric applications due to its very high thermoelectric figure of merit, ZT, with values of 2.6 in p-type and 2.8 in n-type single crystals. Sn has been replaced with various lower group dopants to achieve successful p-type doping in SnSe with high ZT values. A known, facile, and powerful alternative way to introduce a hole carrier is to use a natural single Sn vacancy, VSn. Through transport and scanning tunneling microscopy studies, we discovered that VSn are dominant in high-quality (slow cooling rate) SnSe single crystals, while multiple vacancies, Vmulti, are dominant in low-quality (high cooling rate) single crystals. Surprisingly, both VSn and Vmulti help to increase the power factors of SnSe, whereas samples with dominant VSn have superior thermoelectric properties in SnSe single crystals. Additionally, the observation that Vmulti are good p-type sources observed in relatively low-quality single crystals is useful in thermoelectric applications because polycrystalline SnSe can be used due to its mechanical strength; this substance is usually fabricated at very high cooling speeds