Preparation of Y Doped BaZrO3 Thin Film Electrolyte By Using Laser Chemical Vapor Deposition
Authors: Sakai Takaaki , Kato Tohru , Katsui Hirokazu , Tanaka Yohei , Goto Takashi 
Published: December 2020

It is well known that some cerate based or zirconate based perovskites exhibit proton (H+) conduction at around 600oC [1], and those proton conducting perovskites are expected to be used as electrolyte of proton ceramic fuel cells (PCFCs). Especially, Y-doped BaZrO3 (BZY) has received attention, owing to its higher H+ conductivity than other proton conducting perovskites. However, the densification of BZY basically needs high temperature above 1400oC, leading to a critical problem when the BZY film was prepared on a Ni-based composite electrode; BZY significantly reacts with Ni and forms impurity phase such as BaY2NiO5 during the high temperature sintering [2]. In addition, this impurity phase easily decomposes under H2 atmosphere and causes the critical damage for the cell. D. Han et al. have reported that the BaY2NiO5 impurity phase disappears by heating above 1500oC [4]. However, they also have reported that Y2O3 alternatively appears in the high temperature heating [4]. Thus, a preparation technique that can fabricate thin film at lower temperature, is favorable to avoid the formation of the impurity phase in the case of BZY. Currenlty, the pulse laser deposition (PLD) method has been commonly utilized for the lower temperature deposition of ceramic thin films. However, in the case of PLD, its deposition rate is usually 1 μm/h and its area is several cm2 at best, that is, PLD has a difficulty for the practical use. Besides the PLD method, the laser chemical vapor deposition (LCVD) method, which combines a chemical vapor deposition and laser irradiation, has been proposed as one of the low temperature deposition methods. Recently, Goto et al. have demonstrated the laser chemical vapor deposition of the ceramic thin films at a lower temperature [5,6], and actually, they reported the high-speed deposition of TiN film at several 10 μm/h at 600oC- 800°C [5]. In addition, they demonstrated LCVD on a curved surface and a large surface area [6].
Thus, in this work, the preparation of the BZY film was investigated by using LCVD. The deposited BZY film was characterized by XRD, SEM and EDX, and its properties such as structure and chemical composition were analyzed in detail. As a result, it was revealed that the uniform BZY thin film with columnar structure was successfully deposited by the LCVD method. In addition, the thickness of the BZY film was about 16 μm even though its deposition time was only 10 min, suggesting the high speed deposition of BZY film is possible by using the LCVD.
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