Structural and physical properties of Ba(Fe$_{1-x}$Ru$_x$)$_2$As$_2$ single Crystals*

Single crystals of Ba(Fe$_{1-x}$Ru$_x$)$_2$As$_2$, $x<0.4$, have been grown and characterized by compositional, structural, magnetic and transport measurements. These measurements show that the structural/magnetic phase transition found in pure BaFe$_2$As$_2$ at 134K is suppressed monotonically by Ru doping. Superconductivity is stabilized at low temperatures for $x>0.2$ and continues through the highest doping levels we have been able to produce. The superconducting region is dome like, with maximum T$_c\sim18$K found for $x \sim 0.25$. The phase diagram of temperature versus doping based on our measurements will be compared to those of the Ba(Fe$_{1-x}$TM$_x$)$_2$As$_2$ (TM=Co, Ni, Rh, Pd) series as will the associated changes in unit cell dimension and volume. Since Ru doping does not provide extra electrons, the T-x phase diagram will also be compared with T-P phase diagram of pure BaFe$_2$As$_2$.