The usual replacement for barium carbonate
is strontium carbonate. Whiting is another
candidate, because it is also an alkaline earth.
The final alkaline earth choice is magnesium
carbonate but it produces a more viscous melt
and, in large quantities, promotes crawling.
Only 75% as much strontium carbonate,
by weight, is required, and only 51% as much
whiting.
(David Semler, 2009)

Differences in the aspect of the final products
must be expected. Testing is required before
use.