I don't have one yet. I'm new to this. Why do we need a rug anyways?
Yes, you can definitely use a yoga mat. A rug or mat is not actually essential for prayers, the whole point of it is that where you put your head when prostrating must be clean. Feel free to use a whatever you like to pray on or just pray on the bare floor.
There are only three rules to a prayer place it be clean It be towards the quibla it not be facing or have in front of it any forbidden objects This means you could even pray in the street if you could find a good spot. A prayer rug is optional and usually just makes the first and second rule easier to follow. You'll only place it towards the qibla (most have a compass on them) and you'll only stand on it with wudu so it's almost always clean. You can also place a prayer mat on an unclean/suspect surface to make it pak in most cases.
The place of prayer must be clean from impurities. If the place is clean, you don't need nothing at all. And according to a hadith (sayings of the Prophet (pbuh)) the whole earth had been made a prayer mat (a place of prayer), meaning Muslims can pray anywhere they want, provided the place is clean. But how can one be assure all places are clean? So it became a tradition to use prayers rags. Some Muslims do carry prayer rags with them wherever they go too, because , without much concern about the cleanliness of the place, one can simply spread the rags just anywhere and begin praying. So, yes. You can use a yoga mat. No problem. You can also do yoga exercises too. No problem with that, but avoid saying mantras which can be 'shirk'. Allah knows best.
