As the Piast Dukes were almost all Piast agnates, they often used the same arms, but there is some variation, and the Duchy of Troppau was originally part of Moravia, given to an illegitimate son of the Bohemian King.
Now for the coat of arms
The most common used arms represents Silesia as a whole as well as Lower Silesia
Next comes the arms of Upper Silesia
Lower Silesian Piast dukes adopted a few variations to their arms. One was to dimidate the Silesian arms with argent, an eagle gules. Another was to quarter their arms with chequy argent and gules. I am not sure where they come from, but the Dukes did intermarry with the Ascanians of Brandenburg who used red eagle as their arms.
The first Lower Silesian duchy to become separated from the Piasts was the Duchy of Nysa which was given to a Piast Bishop of Breslau (Wrocław) and remained with the Bishops even as it became part of Bohemia. It was only lost after the Silesian wars. The Upper Silesian Duchy of Siewierz was acquired by the Archbishop of Krakow, however I can't find a record of the Krackow Archbishop using arms for Siewierz. Arms of the Bishop of Breslau:
After Silesia became part of Bohemia, the Kings of Bohemia claimed succession rights, and parts of Silesia began to merge with the crown. They some times used the coat of arms of Silesia, such as this depiction of the arms of Matthias Corvinus
