The Mechanism On The Interfacial Reaction For It-sofcs

Solid oxide fuel cell?SOFC?is a solid electrochemical device,which converts chemical energy into electric power directly.It greatly meets the demand of societies for a low-carbon,clean,sustainable and renewable energy.As a new generation of energy conversion technologies,SOFC has thus attracted great interests in the field of new energy.The development of SOFCs in the intermediate temperature range?IT-SOFCs?is the strategic target of SOFCs technologies.Interfacial reaction between sealing glasses and the adjacent components presents a challenge for the development of SOFCs.Seals often react with metallic interconnect during the operation of SOFCs,which leads to the generation of thermal stress and the formation of cracks at the interface,due to the formation of chromates with high coefficient of thermal expansion.The reaction between boron-containing glass-ceramics and lanthanum-containing cathode results in the formation of LaBO₃ on the surface of cathode and the decomposition of perovskite structure.In order to ensure the stability of sealing glasses,this study focuses on the mechanism on the interfacial reaction.This paper investigates the reaction mechanism by adding different oxides into a bismuth-containing borosilicate glass system.Firstly,the effects of rare earth oxides?La₂O₃ and Y₂O₃?on the structure of sealing glass and the interfacial reaction between sealing glass and other components?e.g.,crofer 22 APU,electrolytes and cathode?have been investigated.The results show that the addition of La₂O₃ and Y₂O₃ significantly improves the glass transition temperature,softening temperature,and the connectivity of Si tetrahedron.The interfacial reaction between sealing glass and Cr-containing interconnect can be effectively reduced by La₂O₃ and Y₂O₃ dopants.The reaction rate decreases significantly with increasing field strength of cations.There are no new phases in the accelerated reaction between ceria-based eletrolytes/LSCF and sealing glasses,indicating the good chemical compatibility of sealing glasses.In addition,La₂O₃-containing glass does not bond well with the crofer 22 APU because of crystallizing too fast;while Y₂O₃-containing glass exhibits good sealing performance.Secondly,the effect of La₂O₃ and ZnO co-dopants on the structure of sealing glass and the interfacial reaction between sealing glass and cell components has been studied.The addition of ZnO improves the densification of glass structure,promotes the[BO₃]?[[BO₄]transition,and reduces boron-containing species volatility from glass effectively.The fraction of Cr⁶⁺ in the glass/Cr₂O₃ couple decreases significantly with increasing ZnO content due to the condensed glass structure.The presence of hardystonite phase,(i.e.,(Ca_0.97Zn_0.03)2(Al_0.63Zn_0.37)-(Si_0.69Al_0.31)₂O₇)at the sealing interface between glass and Crofer 22 APU as well as ceria-based electrolytes held at 700? for 500h,improves the chemical stability of sealing interface.Moreover,the addition of ZnO improves the sealing performance of La₂O₃-containing glass.Finally,the effect of Nb₂O₅ on the sealing glass structure,thermal stability and chemical compatibility has been revealed.The addition of Nb₂O₅ condenses the Si tetrahedral units,promotes the[BO₃]?[BO₄]transition,and enhances the formation of boron-containing phases?Ca₃B₂O₆ and CaB₂Si₂O₈?,resulting in the depressed boron volatility from glass and thus the reduced reaction between sealing glass and LSCF cathode.