The Effect of Some Factors on Ms and Sme in Ce-TZP Ceramics

Abstract

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.