Clearly this is the job for a diode in series on the positive connection. I've done this before and have used just a 1N4001 for the job, but my current project is all SMD parts, so...I'd like to use something I have in my surface mount parts cabinet. All I have in SMD for diodes is Zeners (not good), or Schottkys (STPS140, to be exact).
Not necessarily...there are two methods of using a diode for reverse polarity protection:
1. Stick the diode in series with the rest of your circuit so that current can only flow into your circuit one way.
Advantages: Straightforward, no "resetting" required. Comes into effect "instantly".
Disadvantages: Introduces a voltage drop, diode must handle current draw of circuit (sucks when the circuit draws a lot of current). You CANNOT use a schottky diode since it's reverse leakage current is too much and may still damage your circuit in reverse polarity.
2. Stick the diode in anti-parallel with your circuit and a fuse in series with both the circuit AND the anti-parallel diode. During reverse polarity the diode will produce a short-circuit across the circuit clamping it to a low negative voltage (equal to the forward voltage drop of the diode) until the fuse burns out, thus disconnecting the circuit.
Advantages: Introduces no forward voltage drop. THe diode only needs to be able to handle a short current pulse about double the current draw of the circuit so it can be much smaller (no need for the continuous rating). THis is because it only has to be able to conduct enough current to burn out the fuse which is sized for the current draw of the circuit and most fuses burn out very quickly at double the rated current. After the fuse burns out, all current into the circuit will stop.
Disadvantages: The time taken for the circuit to take protect is longer than the other one since the diode must first turn on to conduct the short circuit current through the fuse. THe fuse will then burn out and need to be replaced. You can use a schottky diode in this situation that would increase the speed. In this case, the small reverse leakage current during normal operation doesn't do any harm since it does not go into your circuit. It does introduce a small negative voltage drop (due to the forward voltage drop of the diode) across your circuit while the short-circuit current is trying to burn out the fuse. Your circuit has to be able to survive this. Agan, a schottky diode will help because it has a low forward voltage drop.
---------
So the simple answer to your question, exactly as you worded it, is
YES, in general, there is a reason you cannot use a schottky diode. If your circuit can tolerate the higher reverse leakage current of a schottky during reverse polarity condition it's good (and the reduced forward voltage drop of the schottky during normal operation also increases efficiency over other diodes). But in general, you cannot.