Phase transitions and structure-property relationships in BaCexTi1-xO3 ceramics

Barium titanate, BaTiO3, owing to its high relative dielectric constant and low losses is the most widely used dielectric ceramic material in the electronic industry. The substitution of Ti4+ with a homovalent ion with formation of BaMxTi1-xO3 (M = Sn, Hf, Zr, Ce) solid solutions has gained large attention from both fundamental and application point of view. These materials are attractive for applications such as high energy density capacitors, tunable microwave dielectrics and electrocaloric effect-based cooling devices [1-3]. BaCexTi1-xO3 solid solution is a model system to investigate the effects of local strain fields, Ce4+ being a much larger ion (r = 0.87 Å, c.n. 6) than Ti4+ (r = 0.605 Å, c.n. 6), but while an abundant literature exists on the solid solutions in which Ti is substituted by Sn and Zr, the effect of the incorporation of Ce4+ at the Ti site has not been systematically investigated yet. This work is a comprehensive study of BaCexTi1-xO3: in fact, it combines macroscopic property measurements and average structure information with complementary techniques sensitive to the local structure, i.e. X-ray Pair Distribution Function analysis and Raman spectroscopy, to gain comprehensive insight on the structure-property relationships. BaCexTi1-xO3 ceramics have been investigated over a broad composition (x = 0.02 - 0.30, the upper limit being very close to the solubility limit) and temperature (100 - 400 K) range. The data provide a detailed picture of the BaCexTi1-xO3 system and a composition-temperature phase diagram will be proposed. [1] V. V. Shvartsman, D. C. Lupascu, J. Am. Ceram. Soc., 95, 1-26 (2012), [2] X. S. Qian et al., Adv. Funct. Mater., 24, 1300-1305 (2014), [3] V. Buscaglia et al., J. Phys: Condens. Matter, 26, 065901 (2014)