I i s tacking sequences o rdering of the intercalate

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Unformatted text preview: temperatures and enthalpy changes of intralayer intercalate order-disorder transitions in Br intercalated graphite using differential 2 s canning calorimetric techniques. superlattice in Ag T iS x 2 Evidence of the silver c ompounds has been observed i ndirectly by Suter ( 23) u sing X-rays and Leonelli ( 37) u sing R aman s pectroscopy and directly by Unger e t . al. ( 21) w ith electron diffraction. P a g e - 21T he silver atoms intercalated in T iS 2 c rystals were found to form a n ordered triangular superlattice with a lattice parameter of d 3 a . 0 T he stacking sequence was a ssumed to be abc in accord with the findings of S cholz ( 31) and L eonelli ( 37). Subsequently the X-ray measurements of Suter e t . a l . ( 2 3 ) on A go.33 T iS2 r evealed the same J3a d3a 0 0 x i ntralayer ordering with an abab . . . s tacking sequence. 2 -4 Sample Preparation and Specifications A gxTiS2 s amples were prepared thermally by heating the appropriate amounts of silver powder a nd T iS evacuated quartz ampoule. p owder in an 2 The silver powder was obtained from Materials Research C orporation.and t he T iS prepared as specified in section 2-2. 2 p owder was Samples of Ag T iS2 X i n the range 0 < x < 0 . 7 w ere prepared by mixing appropriate weight quantities of the silver and T i S 2 p owders (total weight for each sample = 0 . 5 g m.). The mixture was placed in quartz ampoules (typically 1 cm. 0 . D x 7 -12 cm. long) and evacuated ( < l o - * t orr) while heating the ampoule (to 150 C ) wi-th h eating tape to remove excess oxygen adsorbed on the walls of the ampoule ( i n order to prevent the possible formation of T i 0 ) . 2 T he sealed ampoules were then shaken using an assortment of vibrators to obtain a homogeneous mixture of silver and T iS ampoule. 2 p owder in the P age - 2 2 - T wo groups of samples were prepared and labelled group A a nd group B . T he ampoules were then uniformly heated to 800 C a nd 1 0 0 0 C ( for group A a nd group B s amples respectively) for a period of 4 - 8 d ays. The samples were cooled once during the 4 - 8 d ay intercalation period to roo...
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