| With increasing concerns of the environment problems,(K, Na)NbO3(KNN)-based lead-free piezoelectric materials have attracted great deal of interest due to their excellent piezoelectric, ferroelectric and electro-mechanic properties that are comparable to traditional lead-based compounds. In the present work, we attempted to grow lead-free [(Na0.57K0.43)0.94Li0.06][(Nb0.94Sb0.06)0.95Ta0.05]03(NKLNST) thin films on Pt(111)/Ti/SiO2/Si(001) substrates by pulsed laser deposition (PLD). The effects of different processing parameters on the surface morphology, chemical composition, structural and electrical properties of the deposited films were studied. Moreover, fabrication of NKLNST nanotubes by PLD was achieved for the first time. We studied the effects of processing parameters on the structure and morphology of the NKLNST nanotubes, laying a ground for further study on fabrication of high-quality NKLNST nanotubes by PLD.Firstly, NKLNST thin films were fabricated on Pt (111)/Ti/SiO2/Si (001) substrates by PLD with targets incorporating various amounts of excess K and Na, and the effects of varying amounts of excess K and Na in the ceramic targets on the crystal structure and chemical composition of the deposited films were studied, in order to optimize the excess amounts of K and Na. Then the NKLNST target incorporating20mol%excess K and Na was found favorable for forming well-crystallized perovskite phase and compensating the volatile K and Na loss in the resulting films, so we consider it as optimum for further growth of NKLNST thin films.Secondly, the effects of different O2pressures and substrate temperatures during the PLD process on the surface morphology, chemical composition, structural and electrical properties of the resulting films were systematically investigated. The results show that proper O2pressure is essential in suppressing the volatilization of K and Na while maintaining the mobility of the laser ablated particles during the PLD process, and both excess K and Na in the target and proper O2pressure working synergistically can lead to single-phase high-quality KNN-based thin films by PLD. With the NKLNST target incorporating20mol%excess K and Na and1Pa of O2pressure well-crystallized thin films with a single perovskite phase and (001) preferential orientation were obtained by PLD, which showed good ferroelectric properties with a remnant polarization Pr of7.18μC/cm2. On the other hand, proper substrate temperature is the key factor in obtaining NKLNST thin films with good crystallization, dense surface and good electrical properties, and such thin films were obtained at a low O2pressure of0.3Pa while the substrate temperature was650℃.Finally, we have achieved the fabrication of NKLNST nanotubes on Pt (111)/Ti/SiO2/Si (001) substrates by PLD for the first time, and the effects of processing parameters on the NKLNST nanomaterials were investigated. Both the O2pressure and substrate temperature play a critical role in depositing NKLNST nanotubes, and it is favorable to grow nanotubes with high O2pressure and high substrate temperature. Furthermore, post-annealing under the atmosphere of K and Na is essential to improve the crystallization of NKLNST nanomaterials. It is important to control the processing parameters judiciously for the fabrication of nanomaterials by PLD.In summary, we have attempted to find the optimal processing parameters of depositing NKLNST thin films by PLD in this study. It is the first time to use targets incorporating various amounts of excess K and Na to deposit KNN-based thin films, and the processing conditions were different from high oxygen pressures (above10Pa) and high temperatures (above700℃), which were most often used for the growth of KNN-based thin films by PLD. So our work may be a good reference for the judicious choice of PLD parameters for the fabrication of KNN-based thin films. Moreover, fabrication of NKLNST nanotubes by PLD was achieved, which provides a new way to grow KNN-based nanomaterials. |
PDF Full Text Request