Structure of praseodymium and neodymium gallate glasses

The rare-earth gallate glasses R 4Ga6O15, where R denotes Pr or Nd, were prepared using an aerodynamic levitator and laser heating system. The structure was studied by applying the method of isomorphic substitution in neutron diffraction which allows for an identification of the gallium and rare-earth coordination environments. The results give a mean Ga-O coordination number of 4.2(1) at a distance of 1.85(2) A and a mean R-O coordination number of 7.4(2) at a mean distance of 2.38(2) A. The experimental results are consistent with a glass network built from GaO4 tetrahedra and with the presence of GaO6 octahedra at the 10(5)% level.