The effect of compositional modifications on the field-induced phase-transition behavior and dielectric properties of strontium-doped lead zirconate titanate (PZT) ceramics was studied. PZT compositions with different strontium and titanium contents, within the general formula Pb 1-x Sr x (Zr 1-y Ti y )O 3 and located in the tetragonal antiferroelectric (AFE) and rhombohedral ferroelectric (FE) phase fields were prepared by tape casting and sintering. X-ray diffraction and polarization measurements were used to locate compositions suitable for investigation of the field-induced AFE-FE phase transition. The results indicated that a higher Sr 2؉ content decreased the polarization and hysteresis and increased the switching field; a lower Ti 4؉ content decreased the polarization and increased the switching field and hysteresis. A high room-temperature dielectric constant was obtained for compositions near the phase boundary. These results suggest that a combination of both A-site and B-site modifications can be used to tailor ferroelectric properties, such as the switching field and hysteresis, of these strontium-doped PZTs displaying a field-induced AFE-FE phase transition.
As known to all,shape memory behaviour has been observed in a variety of metallic alloys. This phenomenon, however, is not only observed in that field but also in other materials recently, such as in polymers,intermetallic compounds and ceramics, especially in zirconia ceramics.Swain (1] observed the shape recovery of a bent magnesia-partiallystabilized zirconia (Mg-PSZ) bar upon heating above a certain temperature. The maximum deflection which was nearly completely recovered on heating is about 300 jum.Chen et al [2] investigated the pseudoelasticity and shape memory effect (SME) in ceria-stabilized tetragonal zirconia polycrystals (Ce-TZP) containing 12 molt CeO,.Wang et al (3] also observed the SME in Ce-TZP containing 10 molt CeO,.Here we would like to introduce some of results conducted recently in our group on SHE in Ce-TZP ceramics. EXPERIMENTSTwo kinds of zirconia ceramics are chosen for studying: (1) ZrO&-CeO: binary system containing 6 to 10 mol% Ce Oa (2) ZrOB-CeO.-YO, ternary system containing 8 mol% Ce 0, and 0.25 to 0.75 mol% YJ0 3The powder with size of 1-2 jim was sintered between 1450 to 1570 OC. The measurement of Ms temperature was conducted by means of a dilatometer of LK-02 type. The size of specimen is 02 mm X 12 mm.The detecting of SHE was conducted by using uniaxial compression on an Instron testing machine,followed by heating in the dilatometer. size of specimen : 4x4X7 mm heating rate : 12*C/min RESULTS AND DISCUSSION The effect of stabilizers on Ms temperatureExperiment shows that the Ms temperature decreases with increasing mole fraction of ceria or/and yttria. The effect of cooling rate on MsAs shown in figure l,the Ms temperature decreases with increasing, cooling rate of 6,12 and 60OC/min for 6 molt CeO.-TZP and 4,6,8,12,18 and 60 C/min for 8 mol% CeO,-TZP. From these results it may be predicted that a TTT diagram should be established in zirconia ceramics. Figure 2 reveals that the isothermal kinetics curves is of "C" shape.
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