Magnetoplumite type of lithium ferrites substituted by aluminium ions  having general chemical formula Li_0.5Fe_0.5+xAl_12-X O₁₉  (where x = 1 to 6) were prepared by standard solid state reaction method The compounds are in single hexagonal phase without traces of uncertainly ambiguous reflection. From XRD pattern lattice parameters has recorded with increasing doped aluminium element in the range from  a = 5.807 Å to 5.906 Å and c = 22.507 Å to 22.585 Å pertaining the space group P6₃/mmc (No.194). The mass density of the ferrites were found linearly varies and depends upon the mass and volume of sample. The X-Ray density has depends upon the lattice constant and molecular weight of the compounds. The average particle size was also estimated. Electrical properties such as dc conductivity, activation energy were studied. Also, the type of carriers responsible in each was determined from thermoelectric studies. The higher resistivity of the compounds Li_0.5Fe_0.5+xAl_12-X O₁₉ suggests less presence of mixed valency cations on equivalent lattice. While Fe show low value due to the ferrous ions present on the octahedral sites along with ferric ions.