Glassy dynamics of the incommensurate-commensurate phase transition in Zr0.98Hf0.02TiO4 ceramics

The complex dielectric constants of Zr0.98Hf0.02TiO4 ceramics are reported in the frequency range 10(-3)-10(10) Hz for the temperature range 830 degre es C less than or equal to T less than or equal to 860 degrees C, just abov e the commensurate-incommensurate phase transition temperature, T-c. The di sappearance of x-ray satellite reflections at 825 degrees C was used to det ermine T-c experimentally. The dielectric measurements show that a relative ly narrow distribution of relaxation times is present in the ceramics, whic h broadens as the temperature approaches T-c from above. By analyzing the t emperature at which the dielectric constant is a maximum as a function of f requency using the Vogel-Fulcher relationship, an activation energy of 550/-15 k(b), where k(b) is the Boltzmann constant, and an effective freezing temperature, T-f, of 825 degrees C have been determined, confirming that, t o within experimental error, T-f coincided with T-c. The experimental resul ts for Zr0.98Hf0.02TiO4 are interpreted in terms of a possible dipole-glass -like phase that has been proposed for relaxor systems. (C) 1999 American I nstitute of Physics. [S0021-8979(99)05009-4].