“…[118,179,180] For the sake of completion, it is also noteworthy that divalent lanthanides such as Sm 2+ , [181][182][183] Eu 2+ , [184] Tm 2+ [185][186][187][188] and especially Yb 2+ [189][190][191][192] show potential for luminescence thermometry, although their thermal behavior is often not governed by simple Boltzmann statistics anymore, but more complex temperaturedependent excited state dynamics involving a crossover to the 4f n-1 5d 1 configuration. [193,194] Unlike the chemically more challenging examples of divalent lanthanides, Pr 3+ has also recently been introduced as an alternative, more stable luminescent thermometer with the same underlying principle of a 4f 2 -4f 1 5d 1 crossover (with eventual incorporation of thermal ionization into the conduction band). [195][196][197] The presented overview is still by no means complete and demonstrates the extremely rapid evolution of the research field.…”