Sains Malaysiana 38(2): 219-226(2009)

 

Phase Formation and Dielectric Properties of Pentavalent Cation Doped 

Non- stoichiometric Bismuth Zinc Niobate (BZN) Cubic Pyrochlore

(Pembentukan Fasa dan Sifat Dielektrik bagi Kubik Piroklor Bismuth Zink Niobate (BZN) Tak Stoikiometrik yang Didop dengan Kation Penta-valensi)  

 

 

K.B. Tan, C.C. Khaw & Z. Zainal

Chemistry Department, Universiti Putra Malaysia

43400 Serdang, Selangor, Malaysia

 

C.K. Lee

Academic Science Malaysia

902-4 Jalan Tun Ismail, 50480 Kuala Lumpur , Malaysia

 

H. Shaari

Physics Department, Universiti Putra Malaysia

43400 Serdang, Selangor , Malaysia

 

Received:   16 Mei 2008 / Accapted:   24 June 2008

 

 

ABSTRACT

 

In an attempt to synthesize new solid solutions and search for better performance materials, pentavalent cation dopants were introduced into the non stoichiometric BZN cubic pyrochlore, Bi3Zn1.84Nb3O13.84. Extensive solid solutions were formed in Bi3Zn1.84Nb3-xDxO13.84 with limit at x = 3 and 2.6 for D = Ta and Sb, respectively. This illustrates the possibility of cation-exchange solid solutions due to similarity in dopants’ ionic radii. The elemental analysis confirmed the stoichiometry of doped materials with no deleterious Bi2O3  loss.  Ta / Sb doped samples were highly resistive with activation energies ranging from 1.2 - 1.9 eV. Temperature coefficient of capacitance, TCC, decreased from -396 ppm / oC to ~ -180 ppm / oC and ~ -90 ppm / oC for both end members, respectively.

 

 Keywords:   Chemical doping; electroceramics;  pyrochlore; solid solutions

 

 

ABSTRAK

 

Sebagai ikhtiar untuk mengkaji pembentukan larutan pepejal yang baru dan menerokai bahan yang lebih berprestasi, kation penta-valensi telah didopkan dalam piroklor kubik BZN, Bi3Zn1.84Nb3O13.84. Larutan pepejal yang ekstensif telah terbentuk dalam siri Bi3Zn1.84Nb3-xDxO13.84 dengan had x = 3 dan 2.6 untuk D = Ta dan Sb masing-masing. Fenomena ini menunjukkan satu kebarangkalian untuk membentuk larutan pepejal saling-tukar akibat daripada kesamaan jejari ionik. Analisis unsur membuktikan stoikiometrik dan juga tiadanya kehilangan Bi2O3 dalam bahan yang telah didopkan. Sementara itu, bahan yang didop dengan Ta / Sb adalah berintangan tinggi dengan tenaga pengaktifan sekitar 1.2-1.9 eV. Manakala, pekali suhu kapasitan, Tcc merosot dari -396 ppm / oC ke  to ~ -180 ppm / oC and ~ -90 ppm / oC  bagi kedua-dua ahli hujung, masing-masing.

 

Kata kunci: larutan pepejal; piroklor; pendopan kimia; seramik elektronik

 

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