We present results of an experimental study on the effect of the inclusion of ferroelectric thiourea particles in paraelectric amorphous KBr on the ferroelectric phase transition. The phase transition as a function of temperature has been observed with optical second‐harmonic generation (SHG) of infrared light. The Curie temperatureTcshows a minimum as a function of the volume fractionxof thiourea in the composites atx=0.4. We describe the experimentally observed density dependence of the Curie temperature in a phenomenological mean‐field model. ©1995 American Institute of Physics.