AUTHOR=Hussain Fayaz , Khesro Amir , Lu Zhilun , Alotaibi Nouf , Mohamad Ahmad Azmin , Wang Ge , Wang Dawei , Zhou Di 

TITLE=Acceptor and Donor Dopants in Potassium Sodium Niobate Based Ceramics

JOURNAL=Frontiers in Materials

VOLUME=7

YEAR=2020

URL=https://www.frontiersin.org/journals/materials/articles/10.3389/fmats.2020.00160

DOI=10.3389/fmats.2020.00160

ISSN=2296-8016

ABSTRACT=<p>B-site doping in potassium sodium niobate (KNN) with Mn<sup>2+</sup> (<inline-formula><mml:math id="INEQ1" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>M</mml:mi><mml:mo>⁢</mml:mo><mml:msubsup><mml:mi>n</mml:mi><mml:mrow><mml:mtext>Nb</mml:mtext></mml:mrow><mml:mo>″′</mml:mo></mml:msubsup></mml:mrow></mml:math></inline-formula>) and Ti<sup>4+</sup> (<inline-formula><mml:math id="INEQ2" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>T</mml:mi><mml:mo>⁢</mml:mo><mml:msubsup><mml:mi>i</mml:mi><mml:mrow><mml:mtext>Nb</mml:mtext></mml:mrow><mml:mo>′</mml:mo></mml:msubsup></mml:mrow></mml:math></inline-formula>) dopants were soluble but prevented KNN from achieving a high relative density, while Sn<sup>4+</sup> (<inline-formula><mml:math id="INEQ3" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>S</mml:mi><mml:mo>⁢</mml:mo><mml:msubsup><mml:mi>n</mml:mi><mml:mrow><mml:mtext>Nb</mml:mtext></mml:mrow><mml:mo>′</mml:mo></mml:msubsup></mml:mrow></mml:math></inline-formula>) was not soluble in the structure as evidenced by second phase peaks in X-ray diffraction (XRD) traces. However, SnO<sub>2</sub> was an effective sintering aid in KNN-50/50. A-site doping with Sr<sup>2+</sup> (<inline-formula><mml:math id="INEQ4" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>S</mml:mi><mml:mo>⁢</mml:mo><mml:msubsup><mml:mi>r</mml:mi><mml:mrow><mml:mo stretchy="false">(</mml:mo><mml:mi>Na</mml:mi><mml:mo>,</mml:mo><mml:mi mathvariant="normal">K</mml:mi><mml:mo stretchy="false">)</mml:mo></mml:mrow><mml:mo>⋅</mml:mo></mml:msubsup></mml:mrow></mml:math></inline-formula>) up to 1 mol% initially improved dielectric properties but higher sintering temperatures were required for compositions with &gt;1 mol% Sr. Samples with 5% and 7% of Sr-doping completely shifted the transition of T<sub>O–T</sub> to below RT and broadened the T<sub>C</sub> peaks as the relaxor. All Ti-doped and Sr-doped compositions showed an increase in conductivity, manifested as high values of dielectric loss (tanδ). More than 1% of acceptor and donor dopants showed the ionic-type conduction mechanism, while 1% displayed the electronic mechanism as attributed from the strongly frequency-dependent tanδ. In conclusion, these samples have the potential to open up new applications in the field of electroceramics.</p>