Preparation And Properties Of Bi₃TiNbO₉-based High-Temperature Piezoelectric Ceramics

Piezoelectric materials,as a kind of electrical functional materials,can realize the mutual conversion of mechanical energy and electrical energy,and have a wide range of applications in aerospace,petroleum exploration,biomedicine and other fields.The service performance of piezoelectric ceramics has brought new challenges with the development of modern industry,especially in high-temperature fields such as aerospace and energy.Bismuth layered-structure piezoceramics can be used as the preferred material for components in high-temperature piezoelectric sensors and filters.Among them,Bi3TiNbO9 has received much attention due to its high Curie temperature,good fatigue resistance and anti-aging properties.However,the direction of spontaneous polarization is limited by two dimensions determined by its special crystal structure resulting in a low piezoelectric coefficient,which seriously restricts the further promotion of this type of material in the application of hightemperature piezoelectric devices.The current modification methods mainly contain process modification and ion-doping.They can improve the electrical properties,but process modification is costly,while ion modification is not able to accurately modulate the change in properties.Therefore,it is necessary to explore a simple way to improve the piezoelectric properties of Bi3TiNbO9.In this thesis,we selected Bi3TiNbO9 as the research object,and improved its piezoelectric properties by the addition of sintering aids.The effects of the sintering aids on the structural,micromorphology,ferroelectric and piezoelectric properties were systematically investigated,and the main conclusions are as follows:(1)Bi3TiNbO9 ceramics at different sintering temperatures were prepared by conventional solid-phase method,and the best preparation process of the material was explored.The sample sintered at 1050℃ exhibits the optimal ferroelectric and piezoelectric properties.(2)Bi3TiNbO9-xwt%B2O3(0≤x≤1.25)ceramics were prepared by the addition of B2O3.It was found that the addition of B2O3 can enhance the growth of grains,and thereby improve the compactness and insulating properties the samples.The sample with the addition amount of 0.75wt%B2O3 possesses an optimal piezoelectric property.The piezoelectric coefficient is 10 pC/N,which is 5 times as large as that of Bi3TiNbO9.(3)To further improve the electrical properties of Bi3TiNbO9,we prepared Bi3TiNbOg-xwt%BaO-2B2O3(0≤x≤2.5)ceramics.The addition of BaO-2 B2O3 can improve the degree of lattice distortion.The grain size firstly increases and then decreases,while the concentration of oxygen vacancies decreases firstly and then increases with increasing the amount of BaO-2B2O3.As a result,the sample with the addition of 2wt%BaO-2B2O3 exhibits the optimal ferroelectric and piezoelectric properties:Pr=8.67 μC/cm2 and d33=14 pC/N,which is 4 times and 7 times as large as that of Bi3TiNbO9.The improved properties can be ascribed to the increased grain size and reduced concentration of oxygen vacancies.