Structure-property relationships in BaCexTi1-xO3 ceramics and comparison with other BaMxTi1-xO3 systems

The substitution of Ti4+ (r = 0.605Å) with a homovalent ion in BaTiO3 ceramics, with formation of BaMxTi1-xO3 (M= Sn, Hf, Zr, Ce) solid solutions, has gained large attention for applications as dielectric or piezoelectric materials. Ce4+ (0.87Å) is the largest among these M ions, thus BaCexTi1-xO3 is a model system to investigate the effects of local strain on macroscopic properties. We present an extensive investigation of BaCexTi1-xO3 over compositions in the x=0.02-0.30 range combining macroscopic property measurements and average structure information with the local structure analysis. By comparing our results with the available literature, especially regarding Zr and Sn substitution, some general conclusions can be drawn. In fact, the compositions corresponding to the tricritical point and the ferroelectric-to-relaxor crossover in BaMxTi1-xO3 are nearly independent on M, suggesting that, irrespective of the M4+ radius, a critical number of Ti-O-Ti bonds has to be broken before a new "state" is established.