Experimental evidence of high pressure during crystallization of glass - The formation of an orthorhombic high-pressure BaF2 phase

Three different glasses in the system Na2O/K2O/Al2O3/KF/BaF2/SiO2 were crystallized. After cooling, in one sample only cubic BaF2 was detected, in the second sample predominantly the orthorhombic modification was found, and in the third sample, both phases were present. The orthorhombic phase according to the literature is thermodynamically stable only at high pressures. During crystallization, compressive stresses cannot relax and the orthorhombic phase is formed. This is the first experimental evidence of the formation of high pressure during crystallization of glass.