Qunbao Yang

Hydrothermal synthesis of bismuth oxide needles

Bismuth oxide (Bi2O3) needles were fabricated hydrothermally by altering the starting materials, mineralizers, reaction temperature and time. The non-agglomerated Bi2O3 needles with a monoclinic structure were prepared using Bi(OH)3 in an alkali solution. The hydrothermal reaction took place at 120 °C in 0.5 h. The length and aspect ratio (length over diameter) of the needles are in the ranges of 6–70 and 5–16 μm, respectively. With the rising reaction temperature and time, the diameter of Bi2O3 needles increased, while the aspect ratio decreased. The formation mechanism of Bi2O3 needles is discussed in the paper.

Lanthanum distribution and dielectric properties of intergrowth Bi5-xLaxTiNbWO15 ferroelectrics

This work was supported by the Ministry of Science and Technology of China through 973-Project under Grant No. 2002CB613307.

Fabrication of Nanotube Thin Films and Their Gas Sensing Properties

The fabrication process and the growth mechanism of titanium/titania nanotubes prepared by anodization process is reviewed, and their applications in the fields of dye sensitized solar cells, photocatalysts, electrochromic devices, gas sensors, and biomaterials are presented. The anodization of Ti thin films on different substrates and the growth process of anodic titanium oxide are described using the current-time curves. Special attention is paid on the influences of the initial film smoothness on the resulted nanoporous morphologies. The “threshold barrier layer thickness model” is used to discuss the growth mechanism. As a case study for gas sensing, anodized highly ordered nanotube arrays and nanoporous thin films that show porous surface with an average diameter of 25 nm and interpore distance of 40 nm were prepared. Gas sensors based on such nanotube arrays and nanoporous thin films were fabricated, and their sensing properties were investigated. Excellent gas sensing properties were obtained for sensors prepared from these highly ordered nanotube arrays, which present stable response even at a low operating temperature of . Based on our experimental results, “H-induced desorption” mechanism was used for explaining the hydrogen gas sensing mechanism.

Large piezoelectric properties in KNN-based lead-free single crystals grown by a seed-free solid-state crystal growth method

This work was supported by the National Natural Science Foundation of China (NSFC, Nos. 51332009 and 51172257), National Basic Research Program of China 973- Projects (2012CB619406), the CAS/SAFEA International Partnership Program for Creative Research Teams, and Science and Technology Commission of Shanghai Municipality (15ZR1445400). Y.L. appreciates the financial support from the Australian Research Council in the form of Future Fellowship.

Microstructure and Electrical Properties of (K0.48Na0.52)NbO3 – (0.16/5.15)K2.9Li1.95Nb5.15O15.3 Lead-Free Piezoceramics Prepared by Two-Step Sintering Method

The phase structures, microstructures and electrical properties of (K0.48Na0.52)NbO3–(0.16/5.15)K2.9Li1.95Nb5.15O15.3 prepared by conventional method (CM) and two-step sintering method (TS) were studied. All the ceramics show typical tetragonal structure at room temperature. The average grain size of the ceramics sintered by CM is about 20 μm. However, it can be decreased to 1–3 μm by TS, which can provide a large driving force for crystal growth through solid-state crystal growth method (SSCG). Prolonging sintering time will not change the dielectric and ferroelectric properties. Therefore, TS is a promising way to prepare matrix for growing single crystal with chemical homogeneity by SSCG.

Nanostructured Molybdenum Oxide Gas Sensors

In this paper, we present a surface acoustic wave (SAW) gas sensor based on nano-structured molybdenum oxide (MoOx) thin film. The film was deposited onto a 36deg YX LiTaO3 SAW transducer, with an operating frequency of approximately 103 MHz, by thermal evaporation. The nanostructured MoOx film consists of connected nanorods with diameters of less than 100 nm. We compared devices with MoOx deposited by RF sputtering and thermal evaporation and found those with evaporated films have response that are an order of magnitude larger.