no 3-qinglin wang王慶林-hpstar annual report

1、1High-pressure electrical transport propertiesof materials-an impedance approachQinglin Wang (王慶林）Supervisor: Dr. Yanzhang Ma2015.06.052Outline Impedance Spectra (IS) method Experimental techniques Applications3Impedance Spectra methodGXYAmethodbygivingthesystemaperturbation using a sine signal with

2、 small amplitude :1.2.No influence on the system itself;Linearresponsebetweenthesystemand the perturbation.MG=Y/X4Experimental techniquesImpedance measurement: Solartron 1260 + Solartron 12965Applicationsgrain boundary effectmineral conductivityconduction mechanism6Sample 13D impedance of LN at diff

3、erent pressures.Wang, et al., APL 106, 132902 (2015).78Loss tangent of LN at 3.4 GPa and 3.2after pressure release.GPaThedielectricperformanceofthebymaterialcanbeimprovedmodulatingthegrainboundarymicrostructure.Frequency dependence of (a) real and imaginary parts of permittivity and (b) tand for LN

4、at different pressures.9Sample 2Variation of imaginary part of impedance (Z) as a function of frequency under different pressures.The Nyquist plots pressures.of B12As2 under differentWang, et al., JAP 117, 045302 (2015).10(a) Pressure dependence of fg and fgb, (b) the variation of dEa/dP with pressu

5、re. The square and(a) Pressure dependence of Rg and Rgb, (b) the grain boundary contribution to the total resistance.circlecorrespondtothegrainandthegrainboundary, respectively11ThepressuredependenceofspacechargeSchematic double-Schottky barrier model at near grain boundary region. F is the space ch

6、arge potential.potential.There exists a pressure-induced inversion of charge concentration in thespace charge layer at 20.7 GPa of B12As2.12Sample 3Montmorillonitepart of impedance (Z) as aVariation of imaginaryNyquist diagrams of Na-mont under pressures.function of frequency under pressures for Na-

7、mont.Na-mont13Theimpedanceofionicconducionatlowfrequencycan be fitted by:RHIF=(jw)-aZ(1)HIFwbRHIForap=Zcos()(2)HIFwa2andapR=(3) HIFwaZsin()HIF2The simulation of Z at 8.2 GPa and the pressure dependent a.In a solid electrolyte,a often deviate from the ideal case of those liquid. In the case of Na-mon

8、t, the discrepancy can reflect the disordered state of the interlayer structure.14Na-montThepressuredependenceofconductivityandrelaxation frequency of Na-mont.The Nyquist-diagram at 3.7 and 31.9 GPa (data points). The continuous lines represent the simulated spectra.15Summary The ionic and electroni

9、c conduction clarified in LiNbO3 under cesses were The grain boundary effect plays an important role in the transport properties of B12As2 under pressure. Thevariationofelectricalconductivityin themontmorillonitewithpressureisrelatedtodehydration process of the interlayer water.16Acknowl

10、edgement1. Dr. Yanzhang Ma, Junkai Zhang, Yanyan Zhang and Feng Ke from HPSTAR.2.Dr.ChunxiaoGao,YonghaoHan,andCailongLiufromState Key Lab of Superhard Materials, Jilin University.17Publications at HPSTAR (04.04.2014-today):1.Qinglin Wang, Yanzhang Ma, et al., “Mixed conduction and grain boundary eff

11、ect in lithium niobate under high pressure”, Applied Physics Letters 106, 132902 (2015).2.QinglinWang,YanzhangMa,etal.,“HighpressurestudyofB12As2:Electrical transport behavior and the role of grain boundaries”, Journal of Applied Physics 117, 045302 (2015).3.Qinglin Wang, Yanzhang Ma, et al., “High pressure electrical transport behavior in organic semiconductor pentacene”, High Pressure Research 34, 355 (2014).Dandan Sang, Qinglin Wang*, et al., “Electronic and optical properties of4.lithiumniobateunderhighpressure:First-principlesstudy”,ChinesePhysics B, 24, 077104 (2015).Feng Ke, Qinglin W