There is a HIGH voltage diode in microwave ovens. It works with a HIGH voltage cap to get the vacuum tube/magnetron going. The coil chokes the current to limit power.
The caps usually have an internal resistor to drain the charge when you power down the oven, but don't bet your life on it. If you want to salvage those parts, drain the cap by shorting the top tabs with an insulated screwdriver.
Those diodes aren't suitable for blocking diodes on a solar array, unless maybe you had a high voltage series array feeding a gridtie inverter. Radio Shack sells packs of cheap blocking diodes more suited to 12v panels.
http://www.radioshack.com/product/index.jsp?productId=2062591&cp=&sr=1&kw=diode&orig
kw=diode&parentPage=search
would handle a 50 watt panel. There is also a 3amp diode that would handle a 25 watt panel.
