Synthesis And Properties Of PMNT Thin Films Prepared By Sol-Gel Method

As lead magnesium niobate-lead titanate((1-x)[Pb(Mg1/3Nb2/3)O3]-xPbTiO3,(1-x)PMN-xPT)thin films exhibits excellent properties ferroelectric,dielectric,pyroelectric,electro-optical and piezoelectric,it be used as a new type of pyroelectric materials applied in the field of pyroelectric detection.As the low cost,ease of integration with semiconductor and precise control of the chemical composition,Sol-Gel method can be used for the preparation of PMN-PT films.In this paper,PMN-PT films were prepared by sol-gel method,and the process conditions,phase structure,dielectric properties,ferroelectric properties and pyroelectric properties were systematically studied.Moreover,the study on the microstructure prceparation was carried out.The main results are as follows:First,using TiO2 as the buffer layer between Pt and base,the preparation of Pt bottom electrode was carried out by magnetron sputtering method on SiO2/Si/SiO2 substrate.The results show that Pt base presents high(111)preferred orientation,square resistance is 2,8502?/?,the root mean square roughness is 0.5702 nm.The second,the high(100)preferred orientation of 0.7PMN-0.3PT components of thin films were obtained by sol-gel method,the excessive Pb and Mg elements,annealing temperature and annealing time of heat preservation on the impact of the perovskite structure were studied.The grain size of 0.7PMN-0.3PT thin films were observed between 95-105nm and thickness was 500mm with a scanning electron microscope.The electrical test shows that the relative dielectric constant of 1kHz can be up to 1135,the residual polarization intensity is 12.495?C·cm-2,and the coercive field is 45.6kV/cm.Thirdly,the electrical properties of different components(1-x)PMN-xPT(x=0.25,0.36 and 0.40)were compared and analyzed.The results show that 0.75PMN-0.25PT and 0.6PMN-0.4PT in pscudo-cubic and tetragonal structure have large dielectric constant,the relative dielectric constant under 1 kHZ frequency of 1534 and 1800 respectively,when compare the dielectrie-temperature found that in pscudo-cubic structure of 0.75PMN-0.25PT under 10 kHz frequency components appear the phenomenon of the discontinuity.While 0.64PMN-0.36PT and 0.6PMN-0.4PT showed excellent dielectric-temperature characteristics at high frequency.In addition,the effects of the doping of La and Pr two rare earth elements on the properties of 0.7PMN-0.3PT were studied.The results show that both of these elements can improve the electrochemical properties of PMNT films,especially the doping of Pr elements,and the dielectric and ferroelectric properties have been doubled compared with that of undoped.In a certain degree,the doping of La is more inclined to make the PMNT of morphotropic phase boundary to be offset by the pseudo-cubic structure.Finally,the PMNT films were graphed by wet corrosion;then,the deposition of NiCr alloy and Au electrode was carried out by Lift-off technique.The process exploration of the graphing of pyroelectric unit is completed.