A Study On Magnetic Doping And Performance Of Bi_3.15Nd_0.85Ti₃O₁₂（BNT）

Multiferroics is a kind of magnetoelectric material which has achieved great development in recent years. It integrates ferromagnetism and ferroelectricity into one and contains coupling effect between them, and it also has promising prospect on application of information storage, magnetic sensor, and spin-electron devices, integrated devices of capacitance and inductance, as well as microwave technology. However, the present single-phase multiferroics have some problems such as weak coupling effect, or some materials still cannot show strong magnetoelectric coupling effect even at low temperature, and these are the main obstacles for further applications. This paper attempts to explore the Bi3.15Nd0.85Ti3O12(BNT) according to the researches on status-quo of multiferroics, prepare single-phase multiferroics and characterize its multiferroic performance through technology innovation, magnetic doping and new research methods, so as to narrow down the gap between theory and practice. To sum up, this paper aims at studying the synthesis, structure and multiferroic performance of the single-phase multiferroics, and the major findings are as follows:Firstly, this study prepares the ceramic samples of (Bi3.15Nd0.85)(T13-xCox)O12-δ and (Bi3.15Nd0.85)(Ti2FexCo1-x)O12-δ through multi-step solid state reaction methods and characterizes its microstructure and multiferroic performance. The tests of ferromagnetism, ferroelectricity and dielectricity show the concurrence of ferroelectricity and ferromagnetism at room temperature in these samples, so it can be preliminarily concluded that they have magnetoelectric coupling effect.Secondly, this study prepares the film samples of (Bi3.15Nd0.85)(Ti1.5Co1.5)O11.25(BNT-Co1.5) and (Bi3.15Nd0.85)(Ti2Fe0.5Co0.5)O11.5(BNT-Fe0.5Co0.5) through Sol-Gel methods, and characterizes their microstructures and multiferroic performances. The tests of ferromagnetics prove the existence of ferromagnetism in the samples, and then the author further compares them with the ceramic samples prepared by multi-step solid phase methods on magnetic performance, finally the findings show that the remnant magnetization of samples prepared by Sol-Gel methods is seven times stronger than that prepared by multi-step solid state reaction methods, and their coercive field has one lower order of magnitude.Thirdly, this study prepares the ceramic of (Bi3.15Nd0.85)(Ti2.5Co0.5)O11.75and (Bi3.15Nd0.85)(Ti2Fe0.5Co0.5)O11.5through superfine powder methods, and proves the existence of ferroelectricity through the ferroelectric tests and the test of magnetism also shows that it contains great ferromagnetism. This paper also makes a contrastive study on the ferroelectric hysteresis loop and hysteresis loop of BNT-Co0.5ceramic samples prepared by superfine powder methods and multi-step solid phase methods respectively, and finds out that the BNT-Co0.5ceramic samples prepared by superfine powder methods has better multiferroic performance indeed.