Study On The PBSZT Piezoelectric Ceramic Materials With Low Loss And The Preparation Technology Of Its Power Device

The Pb1-a-bBaaSrb(Sn1/3Nb2/3)A(Zn1/3Nb2/3)B TiCZr1-A-B-CO3+xwt.%Mn(NO3)2+ywt.% Sb2O3(PBSZT)piezoelectric ceramic materials with low dielectric loss for high power applications were researched in this thesis. The effects of A-site substitutions with Sr and Ba, dopings with Sb and Mn on the ceramics properties were researched systematically. The ceramics forming technology was rearched as well. By the adjusting of Zr/Ti ratio, A-site substitutions with Sr and Ba, doping with Sb and Mn, the Pb0.9Ba0.05Sr0.05(Sn1/3Nb2/3)0.06(Zn1/3Nb2/3)0.06Ti0.44Zr0.44O3+xwt.%Mn(NO3)2+ ywt. %Sb2O3 piezoelectric ceramics with low dielectric loss were prepared. The low dielectric loss and the mechanical loss were researched. The sintering technology and polarization technology were studied for their influences on the dielectric and piezoelectric properties of the ceramic materials. The high properties and low dielectric loss piezoelectric ceramics were prepared, the propertis of tanδ(%)=0.27,Qm=817, Kp=0.488, d33=293 pC?N-1 andεr=1746 were gained when the doping contents of Sb2O3 and Mn(NO3)2 were 0.2wt.% and 0.3wt.%, respectively. The propertis of tanδ(%)=0.39, Qm=2809, Kp=0.5, d33=270 pC?N-1 andεr=1664 were gained when the doping contents of Sb2O3 and Mn(NO3)2 were 0.2wt.% and 0.5wt.%, respectively. The former is suitable for the application of transmit-receive hydroacoustics transducer for its moderate Qm, and the latter is suitable for the application of transmitting hydroacoustics transducer for its high motivation.The Co2O3 doping experiment results show that the doping have weaker effect on the decrease of the dielectric loss, comparing with the Mn(NO3)2 doping, but have notable effect on the increase of the dielectric constant. The Co2O3 doping have effect on the decrease of dielectric loss while together with Mn(NO3)2 doping. The CeO2 doping have some effect on the decrease of dielectric loss, and bring out better piezoelectric properties.The aging experiment results show that the PBSZT ceramics prepared by A-site subsitution with with 5mol% Sr and 5mol% come with better dielectric constant aging prpperties(δεr=13.9%). The results show that the domain structure and its grain size partially answer for this. The ceramics doped with CeO2 come with better dielectric constant aging prpperties, too. The researches show that the space-charge pin the domain, and optimize the aging properties. The experiment results show the optimizing sintering technology is at 1250℃for 3h with rate of 300℃/h. The polarization experiment results show that the optimization polarization technology of the PBSZT ceramics is polarizing in oil bath at 120-140℃for 30 min in 4-4.5kV/mm electric field.The gelcasting technology was studied systematically. Effects of dispersant ammonium salt of polyacrylic acid (PMAA-NH4), pH value of the suspensions and solids loading on the viscosity of the suspensions were studied. The results show that the optimum concentration of PMAA-NH4 and the optimum pH are 0.30-0.45 wt.%( by weight of the PZT powders) and 8.5-11.0, respectively. the stable suspensions with high solids loading (up to 50 vol.%) and low viscosity (<1Pa·s) was obtained for gelcasting. The sample with more homogeneous microstructure was gotten by gelcasting forming technology than by die pressing forming technolgy.The experiment results show that the tribasic ammonium citrate (TAC) is a effective dispersant for the PZT suspensions, but the PMAA-NH4 has better dispersant effect. The pH value of 10 is good for the dispersion when the TAC is taked as the dispersant. The optimum concentration of TAC is 1.5-2.0wt.%( by weight of the PZT powders). The stable PZT suspensions with high solids loading (up to 50 vol.%) and low viscosity (<1Pa·s) was obtained for gelcasting in the experiment.The PBSZT ceramic specimen by die pressing come with better dielectric constant uniformity of 4.06%. The dielectric and piezoelectric properties of gelcast sample are tanδ=0.25%, Qm=579, Kp=0.510, d33=330 pC?N-1 andεr=1511. The dielectric and piezoelectric properties of die pressed sample are tanδ=0.47%, Qm=2065, Kp=0.515, d33=322 pC?N-1 andεr=1470 at the same sintering technology.The results show that the forming technology affect the properties of Qm and losses obviously. The losses mechanism and the correlation of mechanical and electrical losses of the PBSZT ceramics were studied as well. The result show that the correlation is decided by 90°domain ,and affected by forming and materials composition.