Crystal structures and hydrogenation behavior of (Ca_(0.9)Sr_(0.1))_8(Al_(1-x)Zn_x)_3 alloys

摘要

The crystal structures and hydrogenation behavior of the (Ca_(0.9)Sr_(0.1))_8(Al_(1-x)Zn_x)_3 (x=0,0.2,0.2,0.3 and 0.4) alloys were investigated.The new phase (Ca,Sr)_2(Al,Zn) was found when x(?)0.2.(Ca,Sr)_2(Al,Zn) crystallizes in space group I4/mmm (A-139).The lattice parameters were calculated to be a=b=1.1626(2) nm,c=2.6422(4) nm.Zn atoms occupy the 8h and 16n sites together with Al atoms.The (Ca_(0.9)Sr_(0.1))_8Al_3 alloy only contains a single Ca_8Al_3 phase.The (Ca_(0.9)Sr_(0.1))_8(Al_(1-x)Zn_x)_3 alloys consist of Ca_8Al_3,Ca_5Zn_3,Ca and (Ca,Sr)_2(Al,Zn) phases when x is from 0.1 to 0.3.As x increasing to 0.4,the alloy consists of (Ca,Sr)_2(Al,Zn),Ca_5Zn_3 and Ca.The hydrogenated (Ca_(0.9)Sr_(0.1))_8Al_3 and (Ca_(0.9)Sr_(0.1))_8(Al_(0.9)Zn_(0.1))_3 samples consist of CaH_2 and Al.The (Ca_(0.9)Sr_(0.1))_8(Al_(1-x)Zn_x)_3 (x=0.2,0.3 and 0.4) samples can be hydrogenated into Call_2,Al and CaZn_(13) under a hydrogen pressure of 5 MPa at 473 K.