Research On Theory And Computer Simulation Of Ferroelectric Size Effect

With the improvement of preparation technology, Ferroelectric materials gradually developed in the extent of small size. At the same time, many experiments show that some new phenomenon appears as the minishing size. In some ways, these ferroelectric materials of small size are very different from traditional ceramic materials, even reversed. The changes of performance and property in ferroelectric materials with the small size are defined as ferroelectric phase transition size effect.In this paper, size effect of ferroelectric materials was researched from this point. In order to analyze this problem from different ways, this paper firstly simulated the domain evolvement without long-rang elastic force in the inorganic field. Secondly, Preisach model within magnetic field was used to simulation the ferroelectric hysteresis under the normal distribution. The depolarization-field effect was also researched with different electrode. In the end, in the organic composite field, this paper brought out cut-filled mode to simulate electric parameters of ferroelectric composite films, such as piezoelectric coefficient, pyroelectric constant, and so on.The results show that long-rang elastic force is an important factor during the evolvement of ferroelectric domains. If long-rang elastic force is introduced properly, the 90°, 180°domains of ferroelectric materials will be simulated exactly. When the distribution of ferroelectric domains accords with the normal law, both of spontaneous polarization and coercive field will rise with the increasing of level factor or asymmetry center. Meanwhile, it is found that the better homogeneity of ferroelectric domain is , the better performance is. For the film of ferroelectric composite, Monte Carlo simulation shows that the peak point of pyroelectric constant will appear at the condition of the small rate of particle size to thickness of film and the high volume fraction of ceramic. It provides the theoretical base and direction in the preparing of high-performance ferroelectric films.