German player Mona Barthel struggled with 10 double-faults in a loss to Iga Swiatek as a blinding sun made it nearly impossible to see the ball once she tossed it.
Krejcikova, ranked 33 in the world and playing just her fifth main draw in a Slams singles event, triumphed 6-1, 2-6, 6-4 for a second career title.
For just the second time in the Open era, there are four first-time major semi-finalists in the women's singles, after the 1978 Australian Open.
The 31st-seeded Pavlyuchenkova will make her debut in the final four of a Slam in her 52nd appearance at one after edging her doubles partner, Elena Rybakina, 6-7 (2), 6-2, 9-7 on Tuesday.
Azarenka again took aim at officials following her defeat by Pavlyuchenkova, when asked about the scheduling of the new night sessions -- with six of the seven so far featuring men's matches.