Conventional presintering and reaction presintering processes for the production of ceramic powders yield products exhibiting an undesired primary particle size distribution along with localized distribution of impurities, which give rise to the formulation of undesired duplex structures during final sintering.In order to avoid formation of undesired duplex structures within sintered ceramic parts a process and a device for producing ceramic powders based on single- or multi-phase metal oxides (including SiO.sub.2 - compounds), exhibiting a narrow particle size distribution, i.e. with a maximum deviation of the primary crystal size (REM) of +/- 0.75 .mu.m, preferentially less than +/- 0.25 .mu.m, within an average particle size of 0.05 up to 10.0 .mu.m, is conceived. The raw feed material exhibits a specific surface area of 0.05 up to 500 m.sup.2 /g (BET), preferentially 5.0 up to 50 m.sup.2 /g and is treated in an indirectly heated drop tube furnace in form of classified granules exhibiting an average diameter of 10 up to 2500 .mu.m, preferentially 25 up to 250 .mu.m, for a period from 0.5 up to 15 seconds, preferentially 1.5 up to 5 seconds, at a temperature of 500.degree. up to 3500.degree. K., preferentially up to 2500.degree. K., whereby the raw feed material flows freely into the furnace via a charging device and drops by action of gravity, in a quasi free-falling manner, through the furnace atmosphere, which is oxidizing, inert or reducing. The drop tube furnace has at least one drop tube strand, the temperature profile of each strand is divided into a plurality of temperature zones. A cooling system is disposed after the last heated temperature zone.By using accordingly processed ceramic powders it becomes possible to produce sintered ceramic parts, exhibiting a uniform microstructure, which is essentially free of undesired duplex structures.