The melting temperature of REE oxides is in the range 1690–
2400 1C. Lithium metaphosphate well mixes with the REE oxides in
the batch, wherein the melting point of the mixture reduces. Lithium
has a high cross section of thermal neutrons capturing, lack of heavy
element atoms in the host is also reason to choose lithium metha-
phosphate and the possibility of forming homogeneous optically
transparent glass with the volume of a perfect working surface which
need no mechanical treatment directly in crucibles.