Novel pyrochlores in the Bi2O3–MgO–Ta2O5 (BMT) system: Synthesis optimisation, phase equilibria and dielectric properties
Investigating the phase equilibria within the Bi2O3–MgO–Ta2O5 (BMT) system offers critical insights into the formation and stability of pyrochlore phases. This understanding enables the correlation of dielectric properties with phase equilibria data, facilitating the identification of compositions e...
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Elsevier
2025-06-01
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| Series: | Journal of Science: Advanced Materials and Devices |
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| Online Access: | http://www.sciencedirect.com/science/article/pii/S246821792500019X |
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| author | K.B. Tan P.Y. Tan Y. Feng C.C. Khaw V. Raman H.C. Ananda Murthy R. Balachandran S.K. Chen O.J. Lee K.Y. Chan D. Zhou M. Lu |
| author_facet | K.B. Tan P.Y. Tan Y. Feng C.C. Khaw V. Raman H.C. Ananda Murthy R. Balachandran S.K. Chen O.J. Lee K.Y. Chan D. Zhou M. Lu |
| author_sort | K.B. Tan |
| collection | DOAJ |
| description | Investigating the phase equilibria within the Bi2O3–MgO–Ta2O5 (BMT) system offers critical insights into the formation and stability of pyrochlore phases. This understanding enables the correlation of dielectric properties with phase equilibria data, facilitating the identification of compositions exhibiting optimal performance. Phase equilibria within the BMT system have been investigated across a temperature range of 800–1025 °C. The layouts of compatible triangles, encompassing two-phase, three-phase regions and the single-phase BMT subsolidus solution area, have been determined through qualitative XRD phase analysis of approximately 150 synthesised compositions. The BMT trapezoidal cubic pyrochlore region could be represented by the general formula of Bi3.56-xMg1.96-yTa2.48+x + yO13.50+x+(3/2)y, 0.00 ≤ x ≤ 0.32; 0.00 ≤ y ≤ 0.20. Two formation mechanisms are proposed: (i) compositions of Bi3.56-xMg1.96Ta2.48+xO13.50+x at fixed MgO content, involving a one-to-one substitution of Bi3+ by Ta5+ and oxygen non-stoichiometry x Bi3+ → x Ta5+ + x O2− and (ii) Bi3.56Mg1.96-yTa2.48+yO13.50+(3/2)y at fixed bismuth content, with Mg content reduction proportional to Ta5+ and O2− substitution, i.e. y Mg2+ → y Ta5+ + 3y/2 O2−. Dielectric properties within this extensive subsolidus solution area exhibit variability; specifically, BMT pyrochlores exhibit dielectric constants (ε′) ranging from 70 to 84, dielectric losses (tan δ) in the order of 0.2–9.1 × 10−3, negative temperature coefficients of dielectric constants (TCε′) ranging from 130 to 360 ppm/°C and activation energies (Ea) ranging from 1.10 to 1.48 eV. |
| format | Article |
| id | doaj-art-93f28eca7a88437b84e8d438ee97d9e6 |
| institution | DOAJ |
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| language | English |
| publishDate | 2025-06-01 |
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| series | Journal of Science: Advanced Materials and Devices |
| spelling | doaj-art-93f28eca7a88437b84e8d438ee97d9e62025-08-20T03:12:12ZengElsevierJournal of Science: Advanced Materials and Devices2468-21792025-06-0110210086610.1016/j.jsamd.2025.100866Novel pyrochlores in the Bi2O3–MgO–Ta2O5 (BMT) system: Synthesis optimisation, phase equilibria and dielectric propertiesK.B. Tan0P.Y. Tan1Y. Feng2C.C. Khaw3V. Raman4H.C. Ananda Murthy5R. Balachandran6S.K. Chen7O.J. Lee8K.Y. Chan9D. Zhou10M. Lu11Department of Chemistry, Faculty of Science, Universiti Putra Malaysia, UPM, Serdang, 43400, Selangor, Malaysia; Corresponding author.Department of Chemistry, Faculty of Science, Universiti Putra Malaysia, UPM, Serdang, 43400, Selangor, MalaysiaDepartment of Chemistry, Faculty of Science, Universiti Putra Malaysia, UPM, Serdang, 43400, Selangor, MalaysiaDepartment of Mechanical and Material Engineering, Lee Kong Chian Faculty of Engineering and Science, Universiti Tunku Abdul Rahman, Bandar Sungai Long, 43000, Kajang, Selangor, MalaysiaDepartment of Chemistry, Faculty of Science, Universiti Putra Malaysia, UPM, Serdang, 43400, Selangor, MalaysiaDepartment of Prosthodontics, Saveetha Dental College and Hospital, Saveetha Institute of Medical and Technical Science (SIMATS), Saveetha University, Chennai, 600077, Tamil Nadu, IndiaDepartment of Electronics and Communication Engineering, Adama Science and Technology University, P.O. Box:1888, Adama, EthiopiaDepartment of Physics, Faculty of Science, Universiti Putra Malaysia, UPM, Serdang, 43400, Selangor, MalaysiaFaculty of Science and Marine Environment, Universiti Malaysia Terengganu, Kuala Nerus, 21030, Terengganu, MalaysiaCentre for Advanced Devices and Systems, Faculty of Engineering, Multimedia University, Persiaran Multimedia, 63100, Cyberjaya, Selangor, MalaysiaElectronic Materials Research Laboratory, Key Laboratory of the Ministry of Education & International Center for Dielectric Research, School of Electronic Science and Engineering, Xi'an Jiaotong University, Xi'an, 710049, Shaanxi, ChinaKey Laboratory of Functional Materials Physics and Chemistry of the Ministry of Education, The Joint Laboratory of MXene Materials, Jilin Normal University, Changchun, 130103, Jilin, China; Corresponding author.Investigating the phase equilibria within the Bi2O3–MgO–Ta2O5 (BMT) system offers critical insights into the formation and stability of pyrochlore phases. This understanding enables the correlation of dielectric properties with phase equilibria data, facilitating the identification of compositions exhibiting optimal performance. Phase equilibria within the BMT system have been investigated across a temperature range of 800–1025 °C. The layouts of compatible triangles, encompassing two-phase, three-phase regions and the single-phase BMT subsolidus solution area, have been determined through qualitative XRD phase analysis of approximately 150 synthesised compositions. The BMT trapezoidal cubic pyrochlore region could be represented by the general formula of Bi3.56-xMg1.96-yTa2.48+x + yO13.50+x+(3/2)y, 0.00 ≤ x ≤ 0.32; 0.00 ≤ y ≤ 0.20. Two formation mechanisms are proposed: (i) compositions of Bi3.56-xMg1.96Ta2.48+xO13.50+x at fixed MgO content, involving a one-to-one substitution of Bi3+ by Ta5+ and oxygen non-stoichiometry x Bi3+ → x Ta5+ + x O2− and (ii) Bi3.56Mg1.96-yTa2.48+yO13.50+(3/2)y at fixed bismuth content, with Mg content reduction proportional to Ta5+ and O2− substitution, i.e. y Mg2+ → y Ta5+ + 3y/2 O2−. Dielectric properties within this extensive subsolidus solution area exhibit variability; specifically, BMT pyrochlores exhibit dielectric constants (ε′) ranging from 70 to 84, dielectric losses (tan δ) in the order of 0.2–9.1 × 10−3, negative temperature coefficients of dielectric constants (TCε′) ranging from 130 to 360 ppm/°C and activation energies (Ea) ranging from 1.10 to 1.48 eV.http://www.sciencedirect.com/science/article/pii/S246821792500019XPhase equilibriaDielectricsPyrochloresTantalates |
| spellingShingle | K.B. Tan P.Y. Tan Y. Feng C.C. Khaw V. Raman H.C. Ananda Murthy R. Balachandran S.K. Chen O.J. Lee K.Y. Chan D. Zhou M. Lu Novel pyrochlores in the Bi2O3–MgO–Ta2O5 (BMT) system: Synthesis optimisation, phase equilibria and dielectric properties Journal of Science: Advanced Materials and Devices Phase equilibria Dielectrics Pyrochlores Tantalates |
| title | Novel pyrochlores in the Bi2O3–MgO–Ta2O5 (BMT) system: Synthesis optimisation, phase equilibria and dielectric properties |
| title_full | Novel pyrochlores in the Bi2O3–MgO–Ta2O5 (BMT) system: Synthesis optimisation, phase equilibria and dielectric properties |
| title_fullStr | Novel pyrochlores in the Bi2O3–MgO–Ta2O5 (BMT) system: Synthesis optimisation, phase equilibria and dielectric properties |
| title_full_unstemmed | Novel pyrochlores in the Bi2O3–MgO–Ta2O5 (BMT) system: Synthesis optimisation, phase equilibria and dielectric properties |
| title_short | Novel pyrochlores in the Bi2O3–MgO–Ta2O5 (BMT) system: Synthesis optimisation, phase equilibria and dielectric properties |
| title_sort | novel pyrochlores in the bi2o3 mgo ta2o5 bmt system synthesis optimisation phase equilibria and dielectric properties |
| topic | Phase equilibria Dielectrics Pyrochlores Tantalates |
| url | http://www.sciencedirect.com/science/article/pii/S246821792500019X |
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