Depends how you pack the material and this is is a complex combination of size and shape distribution and chemistry. Take a look in:

October 2nd, 2013 The PSD, zeta potential, and rheology of ceramic materials and ceramic slurries/suspensions

https://www.brainshark.com/malvern/vu?pi=97328853&text=M021507

October 21st, 2015 In pursuit of perfect packing

http://tinyurl.com/gnddyr6

October 6th, 2016 Controlling powder bulk density by optimizing particle size and shape distribution

https://www.brainshark.com/malvern/vu?pi=271602698&b=1&tx=120486&c1=22

And Google 'Dinger-Funk equation'

This depends on the shape of the particles as well as the required properties of the compact

Thanks Alan & Hassan. We are using spherical shape powder. Moulding on straight press machine. Single compaction. Lower side more compact than upper side.

Any advice on binder?

Either cobalt or nickel can be used as binding materials. However, use one of them is also relys on the application of the compact. Both materials can increase the compact toughness in case of ceramic.