Abstract
B-site doping in potassium sodium niobate (KNN) with Mn2+(〖Mn〗_Nb^) and Ti4+ (〖Ti〗_Nb^) dopants were soluble but prevented KNN from achieving a high relative density while Sn4+(〖Sn〗_Nb^) was not soluble in the structure as evidenced by second phase peaks in XRD traces. However, SnO2 was an effective sintering aid in KNN-50/50. A-site doping with Sr2+(〖Sr〗_((Na,K))^•) up to 1 mol% initially improved density but higher sintering temperatures were required for compositions with > 1 mol% Sr. All Ti-doped and Sr-doped compositions showed an increase in conductivity, manifested as high values of dielectric loss (tanδ). More than 1% acceptor and donor dopants showed the ionic-type conduction mechanism while 1% behaved the electronic mechanism as attributed from the strongly frequency-dependent tanδ . Sample with 5% and 7% of Sr-doping completely shifted the transition of TO-T to below RT and broadened the TC peaks as the relaxor. In result, these samples have the potential to open the new application in the field of electroceramics.
Highlights
The aim of this research was to introduce acceptor-dopants (Mn2+, Ti4+, and Sn4+) and donor-dopants (Sr2+) into KNN to see the individual effect of their solubility and structural changes on the electrical properties of KNN-50/50-based ceramics
The X-ray diffraction (XRD) traces from KNN-50/50 doped on the B-site with Mn2+, Ti4+, and Sn4+ are shown in Figures 1, 2
The XRD traces from KNN-50/50 doped with 1% Mn and 1% Ti both appear to be similar, but the shape of 2θ ∼ 45◦ {220}, and {002} peaks shows a slight difference (Figure 1)
Summary
Different properties and effects of dopants on potassium sodium niobate (KNN)-based ceramics have been discussed in many publications (Lin et al, 2007; Lee et al, 2008; Wang et al, 2008; Liu et al, 2009, 2012; Tan et al, 2012; Zhao et al, 2013; Bafandeh et al, 2014; Wu J. et al, 2014; Zheng et al, 2015; Yang et al, 2016; Hussain et al, 2019, 2020). Some groups have discussed potassium oxide and sodium oxide both separately and with doping elements, in terms of electrical properties for KNN-based ceramics (Jaffe et al, 1971; Fluckiger and Arend, 1978; Kodaira et al, 1982; Jenko et al, 2005; Lee et al, 2008; Wang et al, 2008; Zhang et al, 2013; Zhao et al, 2013; Zheng et al, 2015). Fewer studies have been done on acceptor (Akça and Yılmaz, 2015; Rafiq et al, 2015; Chen et al, 2016) and donor (Wu S. et al, 2014; Hrešcak et al, 2017) dopants in KNN to understand its electrical properties.
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