Studies On The Doping Technology And Properties Of Modified Potassium Tantalate Niobate

Potassium tantalite niobate (KTN) have extraordinary electro-optic and pyroelectric effects. As a kind of alternative piezoelectric materials now is focused on the alkaline niobate compounds. But it is difficult to be polarized and deviced because of high conductivity and leakage current. So it is used with restrictions. we explore doping modification technology to solve the problems in the practical application of KTN materials caused by high conductivity and high leakage current. This method will supply a new approach for the practical application of KTN material. In this paper, we decide to improve the performance of KTN through hydrothermal technology that dope Ni²⁺ and W⁶⁺ ions into KTN material. We have produced two kinds of nano-powders in different doping systems which are K_1-x Ni_xTa_0.4Nb_0.6O₃ and KTa_0.4Nb_0.6-xW_xO₃, then made them into ceramic under oxygen-full circumstance. At the same time, we have researched the law in how doping ions and doping content impact the critical structure.We use some testing methods such as X-ray diffraction and raman scatter to characterize and research crystal structure of the doping system. The result show that the high pure and tetragonal KTN nano-powders got in the experiment has realized a replacement that K⁺ and Nb⁵⁺ ions in the A site and B site is respectively replaced by Ni²⁺ and W⁶⁺ ions. It was found that the lattice constant, lattice distortion degree and grain size have a great relativity to the doping content. This is mainly due to the radius difference between replacing and original ion.We can measure and analyze the dielectric, conductivity and leakage current characteristics of KTN ceramic using data acquisition instruments such as sophisticating digital bridge, adjustable DC, Agilent39470A and so on. The experiments show that different tests frequency and doping content of the KTN ceramic have great impact on dielectric constant, dielectric loss and conductivity. With a 1 KHZ frequency, the dielectric constant of two kinds of doping system can reach maximum when doping contents of Ni²⁺ and W⁶⁺ ions are both 0.04 mol. The two max dielectric constants are twice and five times respectively as it of pure KTN ceramic. Study found that the conductivity can reduces half when the doping content of Ni²⁺ and W⁶⁺ ions are 0.05mol and 0.06mol respectively. Doping with Ni²⁺ and W⁶⁺ ions can reduce the leakage current of KTN ceramics effectively. The ceramics leakage current can reach minimum when doping content of Ni²⁺ and W⁶⁺ ions is 0.04 mol and 0.08mol respectively. The impact on the performance of KTN ceramics which is produced by doping is mainly caused by the lattice distortion and the surplus electronics arising from impurities ions.In comparison, We found that the performance is best when doping content of Ni²⁺ and W⁶⁺ ions is 0.04mol and 0.08mol respectively, it can reduce the conductivity and leakage current of KTN ceramics most effectively. It can be polarized and deviced easily and can sweep the obstacle in the practical application of KTN materials.