Manufacturing of lead free transparent piezoceramics by densification and crystallisation of laserfused microspheres

在车辆和机器中，振动会导致噪音排放。为了减少这些影响，应使用带有压电陶瓷执行器的adaptronic系统。目前，压电陶瓷在大多数情况下是含铅系统，如PZT。由于无铅压电陶瓷对环境的危害，引起了科学界的极大兴趣。目前的研究热点是KNN系统。透明的压电陶瓷将被用作例如窗户上的振动阻尼系统。在本提案中，将通过激光熔融研究具有化学计量组成KNN的无定形微球的发展。通过CO2激光器，由于液相微球的表面张力，起始材料将熔化并形成。激光束轮廓清晰，冷却速度快，可防止结晶。将考虑透明度、均匀性、粒度以及玻璃化转变和结晶温度来研究微球。玻璃化转变和结晶之间的温度差被称为动力学窗口，并将用于微球的致密化，以获得具有更大体积的非晶样品。将通过关于材料的压电性质和透明度的限定温度处理来研究材料的结晶。

In vehicles and machines vibrations occur which can lead to noice emission. To reduce these effects adaptronic systems with piezoceramic actuators shall be used. At the moment piezoceramics in most cases are lead containing systems like PZT. Because of the environmental harmfulness there is big scientific interest in lead free piezoceramics. The research focus in the moment are KNN systems. Transparent piezoceramics shall be used e.g. as vibration damping systems on windows.In this proposal the development of amorphous microspheres with stochiometric composition KNN will be investigated via laser fusing. By means of a CO2 laser the starting materials will be melted and form because of the surface tension of the liquid phase microspheres. The well defined laser beam profile leads to high cooling rates which can prevend crystallisation. The microspheres will be investigated considering transparency, homogeneity, particle size as well as glass transition and crystallisation temperature. The temperature difference between glass transition and crystallisation is called kinetic window and will be used for densification of the microspheres to obtain amorphous samples with a larger volume. The crystallisation of the material will be investigated by defined temperature treatments with regard to the piezoelectric properties and the transparency of the material.