Many years ago I did extensive testing of a bunch of about 20 diodes for temperatures from 0º to 100º. Data was recorded manually in a painfully slow process which I tried to make as precise (!) as posible. Diodes fed with constant current sources.
While I do not doubt that it was imprecise for any reasonable standard I concluded that:
* Voltage versus temperature curve was NOT linear between 0º and 100º.
* The curve varied sensibly from diode to diode (they were supposed to be from the same batch) (??).
* The curve had the widest separation from the straight line (0º to 100º) at 26º or maybe 60º... actual details escape to me because my precious notebook was lost in a port abroad. Cannot say why I took it ashore.
Learnt to never bring anything out of my bench again.
All this to say: you will have to calibrate each diode/s you will use.