The frequency dependence of the dielectric response deduced from the a
nalysis of infrared reflection spectra of the BaTaO2N perovskite is re
ported. The results are compared with those of barium titanate and dis
cussed. It is concluded that the substitution of one nitrogen for oxyg
en - together with replacement of Ti-+IV by Ta-+V to ensure the proper
charge balance - appears to cancel the possibility offered by some ox
idic perovskites to observe very high dielectric constants since here
no soft mode behaviour is found.