Joint doping of porous glasses to produce materials with high modifier concentrations

Claim 1

In a method of producing a glass article comprising adding a dopant to a porous glass matrix with interconnective pores by immersing the porous glass matrix in a solution of a dopant to impregnate the porous glass matrix with the solution, precipitating the dopant from the solution within the porous glass matrix, removing solvent and where necessary decomposition products from the porous glass matrix and collapsing the porous glass matrix to a solid form, the improvement which comprises immersing the porous glass matrix in a dopant impregnating solution containing a mixture of dopants to impregnate the porous glass matrix with the solution and form an impregnated porous glass matrix with the following composition: (I) 7 to 25 weight percent of the oxide equivalent of at least one member selected from the group consisting of Pb and Bi, and (II) 1.5 to 9 mole percent of the oxide equivalent of at least one member selected from the group consisting of Cs, Rb, and K.