Disorder study in triammonium hydrogen disulphate (NH4)(3)H(SO4)(2) and its solid solutions (NH4)(3-x)MxH(SO4)(2)

Infrared and Raman spectra of (NH4)(3-x)KxH(SO4)(2), 0 less than or equal t o x less than or equal to 3 (NKHS) alloys have been investigated at room te mperature. An assignment of different bands in terms of the OH group, SO42- and NH:4+ ions is given. The substitution effects have been studied in ter ms of evolution towards order using OH group frequencies, the splittings of the v(1) and v(4)(SO42-) Raman bands and the v(1)(S-OH) Raman band width a nd frequency. The size effect of the alkaline substitute has been studied t hrough comparison between potassium and rubidium salts for the phase x=1.