Dielectric and Structural Investigations of the System BaTiO 3 ‐BaHfO 3

Dielectric measurements and X‐ray diffraction studies were made in the system BaTiO 3 ‐BaHfO 3 for polycrystalline specimens containing from 0 to 30 mole % BaHfO 3 . The maximum in the dielectric constant for each composition in creased as the BaHfO 3 concentration was in creased to 16 mole % and then decreased with further BaHfO 3 additions. Room‐temperature lattice constants and hysteresis loops were meas ured for all compositions. A partial solid‐state phase diagram is suggested for the solid solution area of the system. The phase diagram and the dielectric behavior of the system up to 16 mole % BaHfO 3 are explained on the basis of Devonshire's thermodynamic theory. The ferroelectric‐paraelectric transition in the composition containing 16 mole % BaHfO 3 was essentially of second order and occurred between a ferroelectric rhombohedral phase and a paraelectric cubic phase.