Processing And Electrical Properties Of Low-temperature-sintered Lead Indium Niobate-lead Magnesium Niobate-lead Titanate Ceramics With Cu Doping

Much attention have been paid to the relaxed-based ternary ferroelectric solutionPb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3(PIN-PMN-PT) for the optimumpiezoelectric, electromechanical properties and high Curie temperature, high phasetransition temperature and larger coercive field. However, the sintering temperature ofPIN-PMN-PT ceramics is usually over1200C. Such a high sintering temperaturewould not only cause the absence of Pb by seriously volatilization, but also limit the useof cheap Metal, such as Cu and Ag, for inner electrode on multilayer materials. CuO is acommon low-temperature sintering aids, which can effectively reduce the sinteringtemperature of ceramics. However, reports for Cu-doped PIN-PMN-PT ceramics havenot been found till now. In this thesis, the compositions of PIN-PMN-PT-xCuO%(0≤x≤2) were investigated, and the effects of CuO frit on the sintering behavior, phasecomposition, microsturcture and dielectric, piezoelectric, ferroelectric,electromechanical properties of PIN-PMN-PT ceramics were investigated.First of all, the effects of ternary compositions on the phase and dielectric,piezoelectric, ferroelectric and electromechanical and were investigated. The results ofXRD and Raman spectra for (1-x-y)PIN-xPMN-yPT (x=0.40,0.30≤y≤0.40) ceramicsrevealed that the morphotropic phase boundary of the ternary solution located on theposition of y=0.34,where the specimen exhibited excellent properties: piezoelectriccoefficient d33=505pC/N, planar electromechanical coupling coefficient kp=62.5%;phase transition temperature TRT=117C, the Curie temperature TC=199C, theremanent polarization Pr=32.09μC/cm2and coercive field EC=8.92kV/cm. Moreover, well pyroelectic performance was obtained in the PIN-PMN-PT solutions: thepyroelectric coefficient p was as large as0.050μC/cm2C at room temperature, and thethree major figures of merit Fi, Fvand Fdwas2.00×10-10m/V,0.09m2/C and1.00×10-5Pa-1/2at y=0.34, respectively. All of those make PIN-PMN-PT ceramic potencialapplications in pyroelectric detectors.Choosing the composition of0.26PIN-0.40OMN-0.34PT as the matrix powder, thesintering characteristics and dielectric, piezoelectric, ferroelectric and some otherelectrical properties of PIN-PMN-PT-xCuO%samples with variety Cu doping radioswere investigated. It was found that the sintering-properties were modified due to the generation of liquid-phase sintering mechanism when CuO was added, thesintering-temperatures were reduced by more than250C, a phase transition fromco-existence of rhombohedral and tetragonal to rhombohedral was occurred, grain sizesdecreased, and the samples became denser. It showed superior properties when x=0.5,the relative permittivity εr=2864, piezoelectric coefficient d33=484pC/N, planarelectromechanical coupling coefficient kp=59.7%, coercive field EC=9.61kV/cm,Curie temperature TC=225C, mechanical quality factor Qm=93.58and relative strainS=0.145%at x=0.5. The optimum properties and low sintering temperatue makeCu-doped PIN-PMN-PT a promising candidate for applications of multilayerpiezo-devices with cheap base metal as inner electrode.