Shift of the Curie Point of Barium Titanate Ceramics with Sintering Temperature

Abstract

Definite increases in the Curie point (TC) of undoped and lanthanum‐ (La‐) doped (<0.5 at.%) barium titanate (BaTiO3) ceramics sintered at elevated temperatures in the range of 1300°‐1450°C were observed. Both undoped and 0.3 at.% La‐doped BaTiO3 (chosen as a typical doping concentration to yield semiconducting materials) ceramics showed almost the same TC behavior; their TC values increased by ∼3.5°C as the sintering temperature was increased from 1300° to 1450°C. Semiconducting 0.3 at.% La‐doped materials increased in room‐temperature bulk resistivity and TC with increased sintering temperature. The bulk resistivity of the La‐doped materials, which was obtained from complex impedance analysis, increased from ∼2 omega cm for the material sintered at 1350°C to ∼6 ω cm at 1450°C. The phenomenon of bulk resistivity increase with sintering temperature was observed in the materials with a doping concentration of ≥ 0.2 at.% La, but was not observed in those doped with <0.2 at.% La. The mechanisms of TC and the bulk resistivity increase observed in the present materials with increased sintering temperature are discussed based on various models found in the literature, particularly in terms of the defect chemistry in semiconducting BaTiO3 ceramics and the influence of liquid phases present during sintering.

Properties of lanthanum doped BaTiO3 produced from nanopowders

“…In the previous papers this occurrence was also noticed. Otherwise, some authors [17][18][19] have connected the lowering of T C with grain size decrease and this is in agreement with results obtained in our study.…”

Estudio del mecanismo de compensación de BaTiO₃ dopado con La₂O₃

“…Se observó una leve disminución en la tetragonalidad de las muestras con bajo contenido de La 2 O 3 (0,05%), mientras que para mayores contenidos de lantano se detectó una notable disminución de la tetragonalidad conforme se incrementó el contenido de aditivo. En este caso, las fuertes tensiones mecánicas presentes en los granos de pequeño tamaño estabilizaron al material en un estado principalmente pseudocúbico (11). Estos cambios en los parámetros de tetragonalidad los discutiremos más adelante empleando las ecuaciones de compensación de carga.…”

Physical and dielectric properties of BaTiO3–fluoride–glass systems for nitrogen-fireable embedded capacitors

“…The Curie temperatures of LiF and ZnF 2 were around room temperature or below, while AlF 3 , BaF 2 and CaF 2 exhibited high ones of around 115°C. It is known that the Curie transition temperature in ferroelectric materials can be influenced by many factors including chemical modification, particle size and crystal imperfections [20,21].…”