At the moment, crossfade is only available on the iOS app, but we're working hard to make it available on all devices. Some android beta users can test the feature in the Deezer Labs.
iOS app (only)
- Select Settings
(displayed on the top-right corner on any of your Deezer tabs) - Select Audio
- Scroll down to the bottom
- Adjust the slider
Disabling crossfade
Just set crossfade to zero, using the slider to disable crossfading.