Temperature scaling of ferroelectric hysteresis in hard lead zirconate titanate bulk ceramic

The temperature scaling of the ferroelectric hysteresis was investigated in hard lead zirconate titanate (PZT) bulk ceramic. The power-law temperature scaling relations were obtained for hystersis area 〈A〉, remnant polarization P_r, and coercivity E_C in the forms of 〈A〉∝T^-0.9650, P_r∝T^-0.0261, and E_C∝T^-0.8823, respectively, which are mostly comparable to those of its soft counterpart. The observation that P_r decayed more slowly with temperature than in soft PZT was attributed to the presence of the complex defects in hard PZT. However, the product of P_r and E_C still provided the similar scaling law on the T dependence in comparison with 〈A〉. PACS 77.80.-e; 77.80.Fm; 77.84.-s; 77.84.Dy     

Surface Enhanced Raman Scattering in Graphene Quantum Dots Grown via Electrochemical Process

Graphene Quantum dots (GQDs) are used as a surface-enhanced Raman substrate for detecting target molecules with large specific surface areas and more accessible edges to enhance the signal of target molecules. The electrochemical process is used to synthesize GQDs in the solution-based process from which the SERS signals were obtained from GQDs Raman spectra. In this work, GQDs were grown via the electrochemical process with citric acid and potassium chloride (KCl) electrolyte solution to obtain GQDs in a colloidal solution-based format. Then, GQDs were characterized by transmission electron microscope (TEM), Fourier-transform infrared spectroscopy (FTIR), and Raman spectroscopy, respectively. From the results, SERS signals had observed via GQDs spectra through the Raman spectra at D (1326 cm⁻¹) and G (1584 cm⁻¹), in which D intensity is defined as the presence of defects on GQDs and G is the sp² orbital of carbon signal. The increasing concentration of KCl in the electrolyte solution for 0.15M to 0.60M demonstrated the increment of Raman intensity at the D peak of GQDs up to 100 over the D peak of graphite. This result reveals the potential feasibility of GQDs as SERS applications compared to graphite signals.     

Uniaxial stress dependence of ferroelectric properties of xPMN-(1–x)PZT ceramic systems

Effects of uniaxial compressive pre-stress on the ferroelectric properties of ceramics in the PMN-PZT system are investigated. The ceramics with a formula xPb(Mg_1/3Nb_2/3)O₃-(1-x)Pb(Zr_0.52Ti_0.48)O₃ or xPMN-(1-x)PZT when x=0.0, 0.1, 0.3, 0.5, 0.7, 0.9, and 1.0 are prepared by a conventional mixed-oxide method. The ferroelectric properties under the uniaxial compressive pre-stress of the PMN-PZT ceramics are observed at the stress levels up to 13 MPa using a compressometer in conjunction with a modified Sawyer–Tower circuit. It is found that with increasing compressive pre-stress levels the area of the ferroelectric hysteresis (P–E) loops, the saturation polarization (P_sat), the remanent polarization (P_r), and the coercive field (E_c) decrease. These results are interpreted through the non-180° ferroelastic domain-switching processes. Finally, the calculated differential permittivity for all the xPMN-(1-x)PZT ceramics, except for 0.5 PMN-0.5 PZT, decreases with increasing applied stress. PACS 77.22.Ch; 77.84.Dy     

Air to H2-N2 Pulse Plasma Jet for In-Vitro Plant Tissue Culture Process: Source Characteristics

Plasma Chemistry and Plasma Processing - Plasma agriculture has been considered as a promising solution for sustainable and safe agri-food production. Its applications include germination...