Effects of BNT Addition on the Microstructure and PTC Properties of La-Doped BaTiO3-Based PTCR Ceramics

• Published in: Ferroelectrics Vol. 403; no. 1; pp. 91 - 96
• Main Authors: Wei, Jifeng, Pu, Yongping, Mao, Yuqin, Wang, Jinfei
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Colchester Taylor & Francis Group 01-01-2010; Taylor & Francis
• Subjects: BT-BNT ceramics; Ceramics; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Conductivity of specific materials; Curie temperature; curie temperature (Tc); Dielectric, piezoelectric, ferroelectric and antiferroelectric materials; Dielectrics, piezoelectrics, and ferroelectrics and their properties; Electrical resistivity; Electronic transport in condensed matter; Exact sciences and technology; Ferroelectric materials; Gas flow; Insulators; Lanthanum; Microstructure; Niobates, titanates, tantalates, pzt ceramics, etc; Physics; Positive temperature coefficient; PTCR effect; reoxidation; Solid state; Scanning electron microscopy; Electrical conductivity; Curie point; Binary systems; curie temperature (Tc); Barium titanates; High temperature; BT-BNT ceramics; Temperature coefficient; Lanthanum additions; reoxidation; Bismuth Sodium Titanates Mixed; Sintering; Solid state reaction; PTCR effect; Chemical composition; Microstructure
• ISSN: 0015-0193; 1563-5112
• DOI: 10.1080/00150191003748972

Lanthanum (La) doped BaTiO
3
-(Bi
0.5
Na
0.5
)TiO
3
(BT-BNT) positive temperature coefficient of resistivity (PTCR) ceramics were prepared by a conventional solid state reaction method. The microstructure and PTCR effect of BT-BNT ceramics were investigated by scanning electron microscopy and measurement of resistivity-temperature dependence. The BT-BNT ceramics sintered in a N
2
gas flow possessed low room-temperature resistivity (ρ
RT
< 10
2
Ω·cm) and PTCR effect wasn't remarkable (ρ
max
/ρ
min
< 10); through a proper reoxidation process, the ceramics showed a typical PTCR effect (ρ
max
/ρ
min
> 10
3
) but with a high room-temperature resistivity (ρ
RT
> 10
3
Ω·cm). Room-temperature resistivity increased with the raising content of BNT. The Curie temperature (Tc) of BT-BNT ceramics shifted to 160°C for the 8mol% BNT added. With the addition of 4mol% BNT, the obtained BT-BNT ceramics reoxidized at 950°C possessed ρ
RT
= 10
3
Ω·cm and exhibited a resistivity jump (ρ
max
/ρ
min
> 10
3
) at 150°C. The possible mechanism underlying the PTCR behavior in BT-BNT ceramics was discussed.