Microwave processing of conductive lanthanum nickel oxide films in separated microwave magnetic field

In the present work, lanthanum nickel oxide (LaNiO3, LNO) films were prepared by the sol–gel method. Microwave processing in separated microwave magnetic field (H field) was introduced during pyrolysis and annealing treatments. The heating behavior of LNO films in microwave H field was explored. The effects of microwave processing on the orientation and microstructure of LNO films were investigated compared to those obtained from conventional furnace processing. The results show that the (100)-oriented LNO films can be prepared through microwave processing at pyrolysis stage and annealing stage, even though the film thickness obtained from a single coating is much larger than the grain size. On the contrary, (110)-orientation predominates in the films prepared through conventional furnace processing. Furthermore, microwave annealing is favorable for improving the crystallinity of LNO films and promoting the transition of the transport property from the insulating-type to the metallic-type. The underlying mechanism of the above-mentioned effects is discussed in terms of the heating behavior of amorphous and crystallized LNO films prepared in microwave field.