Yin Qingrui

Piezoelectric electron-acoustic probe (PEAP) and some applications

Abstract Piezoelectric Electron-Acoustic Probe has been built in our lab recently, which is an new technique for imaging and characterization of thermal, elastic and pyroelectric property variations on a microscale resolution. Some electron acoustic photographs for different samples, are presented. The results show that electron-acoustic imaging has its own features over secondary electron imaging. In addition, PEAP with different operation model has important potential applications on ferroelectric semiconductor, ferroelectric thin film, ferroelectric semiconductor integrated device, those are also described.

Nanoscale Thermal Response in ZnO Varistors by Atomic Force Microscopy

We report the application of customer-built scanning thermal microscopy (SThM) based on a commercial atomic force microscope to investigate local thermal inhomogeneity of ZnO varistors. The so-called 3ω method, generally used for measuring macroscale thermal conductivity, is set up and integrated with an atomic force microscope to probe the nanoscale thermal property. Remarkably, thermal contrasts of ZnO varistors are firstly imaged by the SThM, indicating the uniform distribution of spinel phases at triple points. The frequency-dependent thermal signal of ZnO varistors is also studied to present quantitative evaluation of local thermal conductivity of the sample.

Raman Scattering Study of Cubic to Tetragonal Phase Transitions in Mixed System AxBa1-xTiO3

The ferroelectric phase transition with the point group change from m3m to 4mm in the mixed system A x Ba 1-x TiO 3 (A=Pb, Sr) was studied by Raman scattering measurements. The low frequency spectra show strong dependence on both composition and temperature. The square of the soft mode frequency shows a linear dependence on T c . While, in temperature dependence, the soft mode of Pb 0.14 Ba 0.86 TiO 3 slightly decreases towards T c on heating, but the softening is suppressed near T c . Peak frequencies higher than 100 cm -1 are insensitive to both composition and temperature. The mode intensity gradually decreases with increasing temperature. In spite of the fact that all optical modes should be Raman inactive above T c , a few modes are still observed in the spectra.

Measurement of Piezoelectric Coefficients of ZnO Thin Film with Photoacoustic Technique

Piezoelectric coefficients e33, e31 of sputtered ZnO thin films are measured by photoacoustic technique. The obtained values for e33 and e31 are 0.81 C/m2 and -0.43 C/m2 respectively. The theoretical consideration and experimental procedures which were used to evaluate the related coefficients of ZnO thin films are presented as well.

Computer-controlled image acquisition and processed system for scanning electron -acoustic microscopy

Abstract Scanning Electron Acoustic Microscopy(SEAM) with the piezoelectric ceramic sensor is a novel instrument in materials analysis. Normally the signal detected by the sensor is very weak. Signal to noise ratio should be enhanced in order to observe electron acoustic image with good quality. In this paper, the time averaging data acquisition system with computer was described and the data transferred into imaging were processed with a computer. Electron acoustic pictures on PZT-type materials were shown in real time and refined and memorized in computer. Results can also be recalled on the screen at any time.

Piezoresponse Force Microscopy Imaging of Ferroelectric Domains in Bi(Zn1/2Ti1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 Piezoelectric Ceramics

Bismuth zinc titanate dopied lead magnesium niobate-lead titanate[Bi(Zn1/2Ti1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3(BZT-PMN-PT)] piezoelectric ceramics are synthesized by the conventional solid state reaction method. Ferroelectric domain structures and the evolutionary behavior of BZT-PMN-PT ceramics under an external in-plane electric field are investigated by piezoresponse force microscopy (PFM). It is found that the BZT doping has a significant effect on the domain configurations and the domain kinetic behavior of the piezoelectric BZT-PMN-PT solid solution ceramics. Microdomains embedded in the macrodomains, induced by the BZT dopant in the solid solution ceramics, are clearly observed by PFM and their volume increases with increasing amounts of BZT doping. The microdomains of BZT-PMN-PT piezoelectric ceramics exhibit better domain dynamic behavior stability than macrodomains under an external in-plane electric field.

Acoustic Imaging Frequency Dynamics of Ferroelectric Domains by Atomic Force Microscopy

We report the acoustic imaging frequency dynamics of ferroelectric domains by low-frequency acoustic probe microscopy based on the commercial atomic force microscopy It is found that ferroelectric domain could be firstly visualized at lower frequency down to 0.5 kHz by AFM-based acoustic microscopy The frequency-dependent acoustic signal revealed a strong acoustic response in the frequency range from 7kHz to 10kHz, and reached maximum at 8.1kHz. The acoustic contrast mechanism can be ascribed to the different elastic response of ferroelectric microstructures to local elastic stress fields, which is induced by the acoustic wave transmitting in the sample when the piezoelectric transducer is vibrating and exciting acoustic wave under ac electric fields due to normal piezoelectric effects.

Water-Induced Degradation in Lead Zinc Niobate--Lead Zirconate Titanate Soft Piezoelectric Ceramics

Water-induced degradation of lead zinc niobate–lead zirconate titanate (Pb(Zn1/3Nb2/3)O3–Pb(ZrTi)O3) soft piezoelectric ceramics is studied using electrochemical hydrogen charging, in which the silver electrodes of the piezoelectric ceramics constitute a cathode in 0.01-M NaOH solution to evolve hydrogen by electrolysis of water. It is found that with the increasing hydrogen charging time, the resonance impedance increases, the difference between the resonance frequency and the anti-resonance frequency decreases, the spontaneous polarization, the remanent polarization and the piezoelectric coefficient d33 decrease. The degradation behaviour of the soft piezoelectric ceramics can be explained to hydrogen incorporating into the lattice and forming hydroxy (OH−) bonds in the perovskite structure, which prevents the Ti ions from switching and increases the coercive field Ec. The degradation characteristics of the soft piezoelectric ceramics are quite different from that of lead zirconate titanate hard piezoelectric ceramics.

The Observation of Martensite and Magnetic Domain Structures in Ni53Mn24Ga23 Shape Memory Alloys by Scanning Electron Acoustic Microscopy and Scanning Thermal Microscopy

We present observations of martensite variants and ferromagnetic domain structures of Ni53Mn24Ga23 ferromagnetic shape memory alloys with a pure tetragonal martensitic phase by using scanning electron acoustic microscopy (SEAM) and scanning thermal microscopy (SThM). Electron acoustic images show a polycrystalline morphology with martensite variants. Direct coincidence between crystallographic martensitic twin variants and magnetic domains is found. A domain-like structure, obtained by SThM, is firstly reported, and then confirmed by magnetic force microscopy (MFM). The experimental results will be helpful for investigating the local thermal properties of ferromagnets and understanding the relationship between martensite variants and magnetic domains.

Relaxor Behaviour and Ferroelectric Properties of (Li0.12Na0.88)(Nb0.9−xTa0.10Sbx)O3 Lead-Free Ceramics

New lead-free ceramics (Li0.12Na0.88) (Nb0.9−x Ta0.10 Sbx) O3 (0.01×0.06) are synthesized by solid-state reaction method. The dielectric, piezoelectric and ferroelectric properties of the ceramics are studied. The dielectric constant dependence with temperature and frequency of the ceramic specimen with x = 0.04 shows typical characteristics of relaxor ferroelectrics, and the Vogel–Fulcher relationship is fulfilled. The dielectric behaviour and its relation to the phase transition phenomena are discussed. The polarization hysteresis loops at room temperature are also measured.