Study On The Properties And Structure Of Relaxor Ferroelectric PMN-PT-PZ Single Crystals With High T_rt

Lead-based relaxor ferroelectric Pb?Mg1/3Nb2/3?O₃-PbTiO₃?PMN-PT?has attracted much attention due to its excellent piezoelectric and electromechanical performance near the morphotropic phase boundary?MPB?.However,PMN-PT exhibits a low rhombohedral-tetragonal phase transition temperature(T_rt).Above T_rt,properties decrease rapidly,so that the temperature stability of the material is greatly reduced.As a consequence,the low T_rt restricts the application of PMN-PT in high power devices or the devices working at high temperature.On the base of PMN-PT,Zr element can be incorporated to form the ternary system Pb?Mg1/3Nb2/3?O₃-PbTiO₃-PbZrO₃?PMN-PT-PZ?,which is expected to be able to grow bulk single crystals with high quality and high T_rt.Unfortunately,systematic study on PMN-PT-PZ single crystals has been insufficient so far.In this work,?1-x?[PMN-PT?65/35?]-x PZ?x?0.10?ceramics was first synthesized by using the conventional solid state reaction method.It was found that T_rt increased with the increasing of PZ content,showing that Zr may play an important role in expanding thermodynamic existence scope of rhombohedral phase.T_rt had great influence on the performance stability of PMN-PT-PZ ferroelectric ceramics.Remanent polarization,coercive field and pyroelectric coefficient changed abruptly near T_rt.The d33 decreased with the increase of PZ content.The 0.96[PMN-PT?65/35?]-0.04 PZ ceramics showed a T_rt of 100 ?,which could satisfy the working temperature requirement of most devices.In addition,the d33 and kp was 502pC/N and 0.51,respectively,showing that 0.96[PMN-PT?65/35?]-0.04 PZ ceramics was the best composition.PMN-PT-PZ single crystal with high quality and large size?the maximum length was 8mm?was obtained by using 0.95[PMN-PT?65/35?]-0.05 PZ as the nominal component,to avoid the deviation of components due to the incongruent-melting characteristic of Zr.The crystal structure was defined to be rhombohedral phase according to the X-ray diffraction analysis [001]c,[110]c,[111]c single crystal samples were successfully fabricated.All of the three samples had T_rt between 115? and 126?,higher than 100?,in consistent with the ceramics.In addition,we studied the properties of the single crystals with different orientationusing domain structure analysis.[001]c sample had the best performance of ??21 ?,10kHz?=4750 and d33*?21??=1208 pm/V with 4R engineered domain structure.Finally,we made the in-situ observation of domain structures in [001]c sample using PLM and found there was a transformation from rhombohedral to tetragonal phase near T_rt and ferroelectric phase to paraelectric phase near Tm,respectively.Furthermore,in-situ observation of domain structures in [110]c and[111]c samples confirmed the existence of rhombohedral phase at room temperature.