| Relaxor-based ferroelectric single crystals are solid solutions with composite perovskite structure. It is consist of rhombohedral relaxor ferroelectrics and tetragonal ferroelectrics and has a general formula Pb(BiB2)O3-PbTiO3, such as PMN-PT and PZN-PT. Those crystals have wide applications for sensors, transducers and actuators due to their excellent electromechanical properties. However, there still have some problems to be solved. For example, it is difficult to grow large size and high quality crystals, and the crystal exhibits inhomogeneity and complicated domain structures. Those factors limited the practical applications in some way.In this work, we focused on domain structures and phase transition of PZN-PT single crystal. The domain structures are studied by polarized light microscope, high temperature metallurgical microscope, XRD, transmittance spectrum, Raman spetrum. And in the meantime,the evolution of micrdomains in PZN-PTcrystals is discussed. In chapter 1, we introduced the background shortly. In Chapter 2, the research progress was reviewed, including crystal growth,domain structures, optical and piezoelectric properties of PZN-PT crystals. Chapter 3 is experiment,including crystal growth,crystal processing,domains observations and testing of spectra. Chapter 4 is the main part of this paper, domain structures of PZN-PT is investigated.We found that domain structures is the major factor which will influence the crystal transmittance. The evolution behavior of domain structures under thermal cycle is studied by high temperature metallurgical microscope. Two domain structures evolution behaviors are observed, the phenomena of reversible and irreversible domain switching are found. The evidence of monoclinic phase is found by XRD technic, and we give the reasonable explanation of domains evolution. Further, the relation among morphology of domains, phase structures and transmittance is discussed. Finally, the main conclusions of this paper are summarized. |
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