If you mix the right amount of it with baking soda, yes. Cream of tartar plus baking soda equals one type of baking powder.
By itself, not as far as I know.
Reading Wikipedia on “baking powder” reveals that you can get by with “baking soda plus…” lots of different things, but without baking soda, none of the other things (vinegar, cream of tartar, etc) can really work on their own.