Thermal expansion of ammonium bromide, rubidium bromide and rubidium chloride

Abstract

The lattice constants of ammonium bromide, rubidium bromide and rubidium chloride have been determined accurately at different temperatures, using a back-reflection camera, and the coefficients of thermal expansion have been evaluated. The lattice constants of the three compounds at 20 C. are 4.0587, 6.8908 and 6.5898 A respectively. The coefficients of expansion of ammonium bromide and rubidium bromide vary parabolically with temperature according to the equations, a =58.96 10 -6-11.98 10-ST + 35.00 10-1T 2 and a = 38.00 x 10 -6-1.54 10-ST + 4.13 10-1T 2, respectively. The lattice constant of rubidium chloride increases linearly with temperature and the mean coefficient of expansion for the range of temperature 20-190 C. is 38-13 x 10-6/C.