Structural and Dielectric Properties of Lead-Free Sodium Bismuth Titanate (NBT) Ceramics and Their Impedance Spectroscopy Analyses

Year 2014, Volume: 14 Issue: 3, 73 - 78, 01.12.2014

Yağız Özeren Ayşe Berksoy Yavuz Sedat Alkoy Ebru Menşur Alkoy

Abstract

Among lead-free based piezoelectric ceramics with perovskite structure, sodium bismuth titanate based ceramics [(Na0,5,Bi0,5)TiO3 ; (NBT)] have very important piezoelectric properties. However, the polling process of unmodified NBT ceramics is very difficult due to exhibiting high ionic conductivity and large coercive field at room temperature.Therefore, nowadays binary 0,94(Na0,5,Bi0,5)TiO3-0,06BaTiO3 and ternary (Na0,5,Bi0,5)TiO3-BaTiO3-(K0,5,Na0,5)NbO3 systems have been developed to alternative (Pb,Zr)TİO3 ceramics. In this study, the structural and dielectric properties of unmodified NBT ceramics as well as (Na0,5,Bi0,5)TiO3-BaTiO3 (NBT-BT) and 0,92(Na0,5,Bi0,5)TiO3-0,06BaTiO3-0,02(K0,5,Na0,5)NbO3(NBT-BT-KNN) ceramics were investigated in detail. All ceramics were crystallized perovskite structure without any secondary phase which to be observed from X-ray analyzed. The electrical behavior of all ceramics was exhibited with an impedance spectroscopy as a function of frequency from 100 Hz up to 10 MHz. The relative density of NBT, NBT-BT and NBT-BT-KNN ceramics were 94%, 98% and 96%, respectively. The highest dielectric constant of measured temperatures (Tm) in NBT, NBT-BT and NBTBT-KNN NBT, NBT-BT and NBT-BT-KNN ceramics were 328oC, 300oC and 287oC, respectively. Tm point was shifted to the lower temperatures with modification. The dielectric constants of NBT, NBT-BT and NBT-BT-KNN NBT were 646, 1451 and 1487 at room temperature, respectively. © Afyon Kocatepe Üniversitesi

Keywords

Piezoelectrics; Leadfree; NBT; Impedance Spectroscopy

Kurşunsuz Sodyum Bizmut Titanat (NBT) Esaslı Seramiklerin Yapısal, Dielektrik Özellikleri ve Empedans Spektroskopi Analizleri

Abstract

Kurşunsuz sistemler arasında yer alan sodyum bizmut titanat [(Na0,5,Bi0,5)TiO3 ; (NBT)] esaslı seramikler önemli piezoelektrik özelliklere sahiptirler. Ancak, katkısız NBT seramiklerin yüksek iyonik iletkenliğe ve oda sıcaklığında yüksek kalıntı polarizasyona sahip olmaları nedeniyle kutuplanmaları zordur. Bu nedenle günümüzde ikili (Na0,5,Bi0,5)TiO3-BaTiO3 ve üçlü (Na0,5,Bi0,5)TiO3-BaTiO3-(K0,5,Na0,5)NbO3seramik sistemleri (Pb,Zr)TiO3 alternatif sistemler olarak geliştirilmeye çalışılmaktadır. Bu çalışmada, katkısız NBT seramiklerin yanı sıra 0,94(Na0,5,Bi0,5)TiO3-0,06BaTiO3 (NBT-BT) ve 0,92(Na0,5,Bi0,5)TiO30,06BaTiO3-0,02(K0,5,Na0,5)NbO3 (NBT-BT-KNN) seramiklerin yapısal ve dielektrik özellikleri detaylı olarak araştırılmıştır. X-ışınları analizlerinden tüm seramiklerin herhangi bir ikincil faz içermeden perovskit yapıda kristalleştiği gözlemlenmiştir. Söz konusu sistemlerin elektriksel davranışları empedans spektroskopisi yöntemi kullanılarak 100 Hz’ den 10 MHz’e kadar frekansın bir fonksiyonu olarak ortaya konulmuştur. NBT, NBT-BT ve NBT-BT-KNN seramiklerin göreceli yoğunlukları sırasıyla % 94, % 98 ve %96’dır. Dielektrik sabitinin en yüksek olduğu sıcaklık (Tm) NBT, NBT-BT ve NBT-BT-KNN seramiklerde sırasıyla 328oC, 300oC ve 287 oC olarak ölçülmüştür. Yapılan katkılar ile Tm daha düşük sıcaklıklara ötelenmiştir. NBT seramiklerin oda sıcaklığındaki dielektrik sabitleri 646 iken, NBT-BT ve NBT-BT-KNN seramiklerin dielektrik sabitleri sırasıyla 1451 ve 1487’dir

Keywords

Piezoelektrikler, Kurşunsuz, NBT, Empedans Spektroskopisi.

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