the compacts the compacts were heat treated at 650 and 850 u00b0 c in o 2 additionally the powder was also heat treated at 450 650 and 850 u00b0 c in o 2 to compare the surface area of heat treated powders with the starting zno powder table i shows the surface area of powder heat treated at different temperatures the surface area of the powders heat treated at 450 and 650 u00b0 c is similar to that of the starting powder implying that the crystal structure of zno powder hasn 39 t changed during doping and heat treatment and that the doped material is still nano sized it is to be noted that the material heat treated at 850 u00b0 c has lost most of its surface area indicating that the particles have grown in size and are aggregating so that heat treatment at high temperatures should be avoided to avoid losing the nano size of the doped zno powder another experiment was performed to examine if al doping can also be achieved by simply dissolving al no 3 3 in deionized water followed by addition of zno nanopowder in the solution the mixture was ultrasonicated to disperse the zno particles subsequently the powder was dried and compacted into 1 6 cm pellets using similar uniaxial pressures used for the above described experiment again poly vinyl butyral was added to the.