Electrical Properties and Impedance Spectroscopy of Lithium Doped Potassium Sodium Niobate (KNN) Based Ceramics

Year 2014, Volume: 14 Issue: 3, 61 - 66, 01.12.2014

Ayşe Berksoy Yavuz Sedat Alkoy Ebru Menşur Alkoy

Abstract

Among various lead-free piezoelectrics, (K0.5Na0.5)NbO3 (KNN) ceramics have been heavily investigated in recent years due to their high piezoelectric properties, high Curie temperature and their electromechanical properties. However, potassium leaves the structure easily during the sintering process of KNN ceramics. Thus, it becomes rather hard to densify KNN through conventional sintering methods due to potassium deficiency and good electrical properties cannot be achieved. The difficulties related to the densification of KNN ceramics must be overcome to achieve good properties. In this study, the structural and dielectric properties of 4 mol % Li (KL4) and 7 mol % Li (KL7) modified KNN ceramics were investigated. Furthermore, electrical behaviors of KNN ceramics were analyzed using AC impedance spectroscopy from 100 Hz to 10 MHz at various temperatures. The Curie temperatures of KL4 ve KL7 ceramics were measured as 468 oC ve 394 oC, respectively. The orthorombic-tetragonal phase transition shifted below room temperature with 7 mol % Li doping. The dielectric constants of KL4 and KL7 ceramics were measured as 345 and 615 at 100 kHz, respectively. The dielectric loss decreased with Li modification. © Afyon Kocatepe Üniversitesi

Keywords

Piezoelectrics; LeadFree ceramics; KNN; Impedance spectroscopy

Lityum Katkılı Potasyum Sodyum Niyobat (KNN) Esaslı Seramiklerin Elektriksel Özellikleri ve Empedans Spektroskopisi

Abstract

Kurşun içermeyen piezoelektrik potasyum sodyum niyobat (K0.5Na0.5)NbO3 (KNN) yüksek piezoelektrik özellikleri, Curie sıcaklığı ve elektromekaniksel özellikleri nedeniyle son yıllarda yaygın olarak araştırılmaktadır. Ancak, KNN seramiklerin sinterlenmesi esnasında potasyum yapıdan kolayca uzaklaşmaktadır. Böylece yapıda potasyum kaybı oluştuğu için geleneksel sinterleme yöntemi ile yoğunlaşması ve dolayısıyla yüksek elektriksel özellikler elde edilmesi zordur. Amaçlanan yüksek özelliklere ulaşılabilmesi için yoğunlaşma sorununun aşılması gerekmektedir. Bu çalışmada, % 4 mol Li (KL4) ve % 7 mol Li (KL7) katkısı ile üretilen KNN seramiklerin yapısal ve dielektrik özellikleri araştırılmıştır. Ayrıca, KNN seramiklerin elektriksel davranışları farklı sıcaklıklarda empedans spektroskopisi ile 10 Hz-10 MHz aralığında ölçülmüştür. KL4 ve KL7 seramiklerin Curie sıcaklıkları yapılan ölçümler sonucu sırasıyla, 468˚C ve 502˚C olarak ölçülmüştür. % 7 Li katkısı ile ortorombik-tetragonal faz dönüşümü oda sıcaklığının altına ötelenmiştir. KL4 ve KL7 seramiklerin oda sıcaklığındaki dielektrik sabiti değerleri 100 kHz frekansta sırasıyla 345 ve 615 olarak ölçülmüştür. Artan lityum katkısı ile KNN seramiklerin dielektrik kayıp değerleri azalmıştır

Keywords

Piezoelektrikler, Kurşunsuz seramikler, KNN, Empedans spektroskopisi.

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