TY - JOUR
T1 - Temperature-Independent, Large Dielectric Constant Induced by Vacancy and Partial Anion Order in the Oxyfluoride Pyrochlore Pb2Ti2O6-δF2δ
AU - Oka, Kengo
AU - Hojo, Hajime
AU - Azuma, Masaki
AU - Oh-Ishi, Katsuyoshi
N1 - Funding Information:
We thank Prof. Mitsuru Itoh of the Laboratory for Materials and Structures, Tokyo Institute of Technology for help with the dielectric property measurement. This work was supported by JSPS KAKENHI Grant Nos. 26800180 and 16K05731 and the Collaborative Research of Laboratory for Structures and Materials, Tokyo Institute of Technology. The synchrotronradiation experiments were performed at SPring-8 with the approval of the Japan Synchrotron Radiation Research Institute (Grant Nos. 2015A1788 and 2015B1796).
PY - 2016/8/9
Y1 - 2016/8/9
N2 - In mixed-anion systems, partial anion order can be the key to realizing enhanced dielectric properties. A novel A2B2X6X′0.5-type oxyfluoride pyrochlore, Pb2Ti2O5.4F1.2, was prepared through the conventional solid-state reaction. Characterization of the oxyfluoride pyrochlore by synchrotron X-ray diffraction and electron diffraction revealed the existence of partial O2-/F- order at the X site, in which F- is involved in fac-type Ti(O/F)6 coordination, associated with the O2-/vacancy order at the X′ site. Although Pb2Ti2O5.4F1.2 adopts a centrosymmetric structure, the refined occupancy factors suggested the existence of local polarization. Partial O2-/F- anion order stabilized the large displacement of Ti4+, leading to a high dielectric constant (as high as 800) with a low-temperature coefficient. These results suggest that mixing heteroanions in pyrochlores provides a basis for exploring novel dielectric materials.
AB - In mixed-anion systems, partial anion order can be the key to realizing enhanced dielectric properties. A novel A2B2X6X′0.5-type oxyfluoride pyrochlore, Pb2Ti2O5.4F1.2, was prepared through the conventional solid-state reaction. Characterization of the oxyfluoride pyrochlore by synchrotron X-ray diffraction and electron diffraction revealed the existence of partial O2-/F- order at the X site, in which F- is involved in fac-type Ti(O/F)6 coordination, associated with the O2-/vacancy order at the X′ site. Although Pb2Ti2O5.4F1.2 adopts a centrosymmetric structure, the refined occupancy factors suggested the existence of local polarization. Partial O2-/F- anion order stabilized the large displacement of Ti4+, leading to a high dielectric constant (as high as 800) with a low-temperature coefficient. These results suggest that mixing heteroanions in pyrochlores provides a basis for exploring novel dielectric materials.
UR - http://www.scopus.com/inward/record.url?scp=84981328321&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84981328321&partnerID=8YFLogxK
U2 - 10.1021/acs.chemmater.6b02509
DO - 10.1021/acs.chemmater.6b02509
M3 - Article
AN - SCOPUS:84981328321
SN - 0897-4756
VL - 28
SP - 5554
EP - 5559
JO - Chemistry of Materials
JF - Chemistry of Materials
IS - 15
ER -