Yixi Yang

Graphene/MnO2 composite prepared by a simple method for high performance supercapacitor

MnO2 nanoparticles are anchored on the graphene nanosheets and make a graphene nanosheets/MnO2 (GMn) composite by thermal decomposition for application in supercapacitor. The GMn composite exhibits specific capacitance of 450 F g− 1 at 1 A g− 1, which is more than three times higher than that of as-prepared graphene sheets. Meanwhile, the composite shows excellent cycle stability without decline over 5000 cycles. The high electrochemical performance of the GMn electrodes is attributed to the prevention of graphene aggregation by the MnO2 nanoparticles, and the synergistic effects between graphene and MnO2 nanoparticles.

Influence of B2O3/SiO2 Ratio on the Fabrication of Nd:YAG Ceramics

B2O3/SiO2 are used as composite sintering aids to fabricate Nd:YAG ceramics by solid-state reaction and vacuum sintering method at 1750°C for 5h using Nano-Al2O3, Y2O3, Nd2O3 as starting materials. In this article, we focus on the influence of B2O3/SiO2 ratio on grain size, porosity and relative density. Finally, with the increase of B2O3/SiO2 ratio, the density and shrinkage rate of transparent ceramics increase, the grain size becomes uniform and the porosity reduces, for the reason that B3+ begins to vaporize at 1300°C and is reduced to trace levels by 1600°C. The best B2O3/SiO2 ratio is 4: 1.

Influence of oxygen partial pressure on the properties of PZT thin film deposited by RF magnetron sputtering

Abstract In magnetron sputtering systems, lead-zirconium-titanium oxide (PbZr1−xTixO3 or PZT) thin films were prepared in a mixture atmosphere of Ar and O2 with various oxygen partial pressures (0, 0.5, 1, 1.5 and 2% oxygen). About 600 nm PZT ferroelectric thin films were deposited on substrates, and then annealed at 600°C for 35 s. The structural, electrical and ferroelectric properties of PZT films were studied. As the oxygen partial pressure increased, the remanent polarisation rose first and went down later, and the leakage current density decreased first and then increased. At the oxygen partial pressure of 0.5%, we obtained the largest remanent polarisation and the minimum leakage current density. The XRD diffraction spectrum of all films displayed predominant (111) preferred orientation, and there was a weak XRD diffraction peak of pyrochlore phase in the PZT films deposited in pure Ar.

Preparation of (100) oriented Sc-doped AlN film on flexible substrate under different pressures using RF reactive sputtering

Abstract Sc-doped AlN films with (100) orientation have high surface acoustic wave velocity and excellent optical properties. Sc-doped AlN thin films based on flexible substrate were prepared by RF reactive magnetron sputtering at pressure levels ranging from 0.3 Pa to 1.5 Pa. The sputtering rate, crystal quality, and electric properties of the Sc-doped AlN films were investigated. The results show that pressure greatly influences the preparation of Sc-doped AlN thin films. Under low pressure, (002) oriented Sc-doped AlN film was prepared; with increasing pressure, the fraction of the (100) plane increased. Furthermore, the electrical properties were closely related to the crystal quality, achieving a maximum resistivity of 3.5 × 1012 Ω · cm, a minimum leakage current of 0.65 × 10−8 A, and a maximum piezoelectric response of 5.2 pC · N−1.

Parameter Optimization for Preparing c-Oriented ScAlN Thin Films

Sc doped AlN (ScAlN) films with c-axis orientation have a very high acoustic velocity and other advantages which could be used for film bulk acoustic resonator (FBAR), surface acoustic wave (SAW) and other piezoelectric devices. In this paper, ScAlN films were prepared by reactive direct-current magnetron sputtering. The degree of preferential orientation (PO), the surface topography and cross-section views of ScAlN thin films grown on Si (100) substrates at various sputtering pressure, sputtering power and substrate temperature have been investigated by X-ray diffraction, atomic force microscopy and scan electron microscope respectively. Results show that the sputtering parameters have significant effects on the PO of ScAlN thin films. The optimum properties that the full width at half maximum (FWHM) of rocking curve of 1.8° and the RMS roughness of 1.811 nm were acquired with sputtering pressure of 0.45 Pa, sputtering power of 130 W, substrate temperature of 600 °C respectively.