Sains Malaysiana 29: 201-209 (2000)                                                                          Sains Fizis dan Gunaan /

        Physical & Applied Sciences

Microstructure, Hardness and Superconducting Properties

of Ag Added ErBa₂Cu₃0_7-δ

Ahmad Kamal Yahya & Faizah Md. Salleh

Faculty of Science

Universiti Teknologi MARA

40450 Shah Alam, Selangor D.E., Malaysia

Abd-Shukor, R.

School of Applied Physics

Universiti Kebangsaan Malaysia

43600 UKM Bangi, Selangor D.E., Malaysia

ABSTRACT

The effect of Ag addition (0-25 wt. %) on the superconductivity, microstruc­ture and hardness of ErBa₂Cu₃0_7-δ (Erl23) was investigated. A sudden drop in the room temperature electrical resistivity was observed when Ag was added. For the 5 wt % Ag content, a significant increase in T_{c zero} (zero-­resistance temperature) from 88 K (pure sample) to 91 K was observed. The increase in T_c was explained in terms of possible increase in oxygen content. However, T_{c sifar} remained approximately constant at 91 K for further addition of Ag (10, 15 and 20 wt. %). At 25 wt. % Ag, T_c zero drops drastically to 69 K. X-ray powder diffraction, Energy Dispersive X-ray Analysis (EDAX) and Scanning Electron Microscopy analysis indicate that Ag did not substitute in the Er123 lattice but instead resides between grain boundaries. Vickers Hardness measurements showed optimum hardness at 15 wt. % Ag content. The increase in hardness was due to the changes in the microstructure of the material.

ABSTRAK

Kesan penambahan Ag (0-25 % bt.) ke atas kesuperkonduksian, mikrostruktur dan kekerasan ErBa₂Cu₃0₇-_δ(Er123) telah dikaji. Penurunan mendadak kerintangan elektrik pada suhu bilik dicerap apabila Ag ditambah. Bagi kandungan 5 % bt. Ag, satu peningkatan bererti T_{c sifar} (suhu rintangan sifar) dari 88 K (sampel tulen) ke 91 K dicerap. Peningkatan T_c diterangkan berdasarkan kemungkinan pertambahan kandungan oksigen. Bagaimanapun, T_{c sifar} hampir kekal malar pada 91 K bagi penambahan Ag selanjutnya (10, 15 and 20 % bt.). Pada 25 % bt. Ag, T_{c sifar} jatuh mendadak ke 69 K. Pembelauan serbuk sinar-X, Analisis Tenaga Serakan Sinar-X (EDAX) dan analisis Mikroskop Imbasan Elektron menunjukkan bahawa Ag tidak menggantikan unsur dalam kekisi Er123 tetapi menempat di antara sempadan butiran. Pengukuran Kekerasan Vickers menunjukkan kekerasan optimum pada 15 % bt. kandungan Ag. Pertambahan kekerasan disebabkan perubahan dalam mikrostruktur bahan.

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