The dependence of thermo-mechanical, and mechanical properties on various rare earth dopants (RE) including Nd2O3, Er2O3, and Yb2O3 in 0.4MgF(2)-0.4BaF(2)-0.1Ba(PO3)(2)-0.1Al(PO3)(3) glasses (MBBA system) is systematically investigated. MBBA system doped with RE dopants presented the potential application in the field of communication and high power layer system in the previous reports. In this work, it is found that the density of the doped glass increases with an increasing of RE concentration, which could be understood in terms of cationic field strength (CFS) effect. The Knoop hardness is found to decrease with the loading time and dopant concentration due to the indentation size effect (ISE) effect. The observed decrease of thermal expansion coefficient and the increase of glass transition temperature T-g with increasing dopant concentration are elucidated in terms of the increasing number of strong covalent bonds with increasing RE dopant concentration. Those results will be of paramount importance before designing optical devices.