Shimin Wang

Synthesis and optical properties of highly c-axis oriented Bi4Ti3O12 thin films by sol-gel processing

Abstract Highly c -axis oriented Bi 4 Ti 3 O 12 thin films have successfully been prepared on fused quartz substrates by sol-gel processing. The orientation degree of the thin film was about 87%. The thin film exhibits good optical transmission. The optical-absorption properties of the thin films have been measured. The variation of bandgap with annealing temperature is studied.

Microstructure and ferroelectric properties of sol-gel derived Bi3.15Nd0.85Ti3O12 thin films on Pt∕Ti∕SiO2∕Si(100)

Bi3.15Nd0.85Ti3O12 (BNdT) thin films were deposited on Pt∕Ti∕SiO2∕Si substrates using a sol-gel process. The film annealed at 750°C is composed of grains of 50–100nm in diameter. The fine grains show nearly random orientations. “Micropores” were frequently observed at the junctions of the grains and they are mostly amorphous, while sometimes containing very fine crystalline particles with sizes of only a few nanometers. The BNdT film capacitors with a Pt top electrode showed excellent ferroelectric properties. The remanent polarization and the coercive field were in the range of 41–43μC∕cm2 and 70–84kV∕cm, respectively. The BNdT capacitors did not show any significant fatigue up to 5×109 switching cycles at a frequency of 1MHz.

Preparation of KTa0.65Nb0.35O3 thin films by a sol-gel process

Abstract Crack-free and transparent potassium tantalate niobate (KTN) KTa 0.65 Nb 0.35 O 3 thin films of perovskite structure were prepared through spin-coating using a sol-gel process. A homogeneous and stable precursor solution was obtained from K(OC 2 H 5 ), Ta(OC 2 H 5 ) 5 , and Nb(OC 2 H 5 ) 5 in absolute ethanol without any additives. Infrared absorption spectra indicate the existence of a complex reaction resulting in the formation of double metal alkoxides KNb(OC 2 H 5 ) 6 and KTa(OC 2 H 5 ) 6 in solution. The precursor powder crystallized to pyrochlore at 600°C, and then completely transformed to perovskite at 750°C. Highly oriented KTN films possessing a perovskite structure were successfully prepared on R -plane sapphire substrates at 750°C and on SrTiO 3 (100) substrates at 650°C. The chemical composition of the KTN films is in good agreement with the atomic ratio of the starting materials.

Synthesis and ferroelectric properties of c‐axis oriented Bi4Ti3O12 thin films by sol‐gel process on platinum coated silicon

c‐axis oriented Bi4Ti3O12films have been prepared on Pt/Ti/Si(111) substrates by sol‐gel process. Crack‐free films of 0.5 μm thickness were fabricated using a multilayer spinning technique and calcination at 600u2009°C for 30 min. The average grain size of the film is about 0.15 μm. The film exhibits ferroelectric hysteresis with remanent polarization Pr=4.8 μc/cm2 and coercive field Ec=70 kV/cm. The measured dielectric constant and loss factor at a frequency of 100 kHz are 170 and 0.02 respectively.

Preparation of highly oriented KTN/SrTiO3(111), KTN/SrTiO3(100) thin films by Sol-Gel method

Abstract Abstarct Highly oriented perovskite KTN/SrTiO3(100)thin films were perpared by Sol-Gel method from KOCOCH3, Ta(OC2H5)5 and Nb(OC2H5)5. The crystallization process of KTN thin films on SrTiO3 substrate was studied by XRD. Some technical parameters such as the solution concentration, viscoaity, catalyst, heat treatment temperature, heating and cooling rate, and O2 flow were determined by the experiments, at the same time, the lattice constant, thermal expansion coefficient and chemical stability of substrate which influenced the structure and quality of KTN films were also discussed

Thermal decomposition of ktn gel and formation of perovskite structure KTN

Abstract This paper reported the thermal decomposition process of KTN Gel and the formation process perovskite structure KTN. Two pyrochlore phases formed in the heat treatment process, one was potassium-deficient pyrochlore phase K3Ta5O14 • 5H2O, another was potassium-rich pyrochlore phase K3Nb2O6(O, OH) • nH2O. The transformation of two pyrochlore phases and perovskite structure KTN were influenced by the potassium content and the heat treatment temperature. The pyrochlore phases readily formed at a lower temperature, at a higher temperature (680°C-750°C), the pyrochlore phases transformed to the pure perovskite structure KTN, but the perovskite structure KTN would decompose to form potassium-deficient pyrochlore phases Ta2O5 • n(KTaO3)(n=2, 3, 4) with the temperature gone np(>950°C). When potassium was excess in the starting materials, the transformation temperature of the pyrochlore phases to perovskite phase was higher, even at 1200°C. When K/Ta, Nb < 1 in the starting materials, the pure perovskite ...

Study of the reactions in preparing ultrafine KTN powders by sol—gel method

Abstract Abstract This paper reported the ractions in preparing ultrafine KTN powders by Sol—Gel method, and discovered that. In the heat treatment process, Gel not only occured the carbonized, oxidized reactions of ethyoxy and the carbonates formation reactions, but also occured the two intermediate phases formation reactions, the formation reaction of KTN phase in one step, and the reaction that the two intermdiate phases reacted with each other to form KTN phase.

The effect of doping Sb2O3 in high d33 • g33 PZT piezoelectric ceramics

Abstract The effect of doping Sb2O3 in Pb(Zr0.54 Ti0.46)O3 is that the tetragonal degree (c/a)of PZT materials can be adjusted. The experiments indicate that the tetragonal degree (c/a) existes an optimum value after doping Sb2O3 in PZT, correspondently, high piezoelectric activity material with d33 = 570 × 10-12C/N,g33 = 32 × 10-3V M/N can be obtained

Effect of substrates and bottom electrodes on the formation of KTN thin film

Abstract This paper reports the preparation of KTN thin films on monocrystalline Sr-TiO3(111), SrTiO3(100), MgO(100) and Si(100) substrates, SiO2 glass substrate, Polycrystalline transparent conducting SnO2(Sb) bottom electrodes (on SiO2 glass) by the Sol-Gel method. The effects of the chemical stability, structure and thermal properties of substrate and bottom electrode materials on the formation of KTN thin films are discussed and it is explained why the pyrochlore phases films on MgO(100), Si(100), SiO2 substrates and SnO2(Sb) bottom electrodes could not be transformed to on the perovskite structure KTN films. Highly oriented KTN thin films of perovskite structure were successfully prepared on SrTiO3(111) and SrTiO3(100) substrates by the Sol-Gel method.

Correlation and comprehensive selection of the piezoelectric ignition material parameters

Abstract Piezoelectric ignition voltage and energy formula is derived from piezoelectric equations, the correlations of energy and piezoelectric material parameters are analysed by electromechanical coupling relation, and general conclusions about comprehensive selection of piezoelectric ignition material parameters are given, also