Yiqing Lu

SrAl2O4: Eu2+, Dy3+ phosphors derived from a new sol-gel route

The SrAl 2 O 4 :Eu 2+ , Dy 3+ phosphor powders were prepared by a new sol-gel method using aluminum isopropoxide and strontium acetate as precursors. The sol-gel process and the structure of the phosphor powders were investigated by means of DSC-TG and XRD. It was found that the single-phase SrAl 2 O 4 was formed at 900 °C, which is 300 °C lower than that required for the conventional solid-state reaction. The particle morphology, photoluminescence and afterglow properties of the phosphors were studied in this article.

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.

Morphotropic Phase Boundary and Electrical Properties of (Bi1/2Na1/2)TiO3-(Bi1/2K1/ 2)TiO3- (Bi1/2Ag1/2)TiO3 Ceramics

The structural, dielectric, ferroelectric and piezoelectric properties of 0.90[x(Bi 1/2 Na 1/2 )TiO 3 -(1-x)(Bi 1/2 K 1/2 )TiO 3 ]-0.10(Bi 1/2 Ag 1/2 )TiO 3 (BNKA) ceramics were studied for the compositional range, x = 0.73–0.89. The morphotropic phase boundary (MPB) composition of the system appears to be near BNKA-79 according to the results of the X-ray diffraction. The optimal piezoelectric properties are observed in the MPB region. The sample with x = 0.79 showed the highest piezoelectric constant d 33 = 160 pC/N. The maximum electromechanical coupling factors, k p and k t , are 0.30 for BNKA-79 and 0.42 for BNKA-85, respectively.

The Formation Mechanism of Intergrowth Bismuth Layer-Structured Ferroelectric Bi4Ti3O12-CaBi4Ti4O15

The formation behavior of Intergrowth Bismuth Layer-Structured Ferroelectric (IBLSF) Bi4Ti3O12-CaBi4Ti4O15 is investigated through conventional solid-state reaction method using Bi2O3, TiO2, CaCO3 as initial powders. The mixed powders are treated from 550°C to 1000°C at 100°C intervals after being milled. The phase transition and thermal behavior of the powders are determined by X-ray diffraction (XRD) and TG/DSC. The results indicate that the compound is mostly changed to Bi4Ti3O12 at 700°C, as calcinating temperature rise to 800°C the intergrowth phase Bi4Ti3O12-CaBi4Ti4O15 (BiT-CBT) forms. When the calcinating temperature rises above 900°C, the BiT-CBT phase is obtained finally. The formation mechanism of BiT-CBT phase will be very helpful for deep understanding of the structures and ferro- and piezoelectric properties of IBLSFs.

Microstructure and Electrical Properties of Lead-free Piezoelectric Ba-excess (Ba0.85(1+0.7%)Ca0.15)(Ti0.9Zr0.1)O3 Ceramics by Microwave Sintering

Microwave sintering was applied to manufacture fine-grained Ba-excess (Ba0.85(1+0.7%) Ca0.15)(Ti0.9Zr0.1)O3 (BCTZ) lead-free piezoceramics from nanometer grinded 0.20 μm particles. The sintering condition dependences of microstructure, density, dielectric constants and piezoelectric properties were investigated. With increasing microwave sintering temperature or soaking time, grain size increases as well as piezoelectric properties. The grain size of BCTZ ceramics by microwave sintering and subsequent high temperature treatment homogeneously increases and the samples show much better piezoelectric properties than those without high temperature treatment.