Dielectric and piezoelectric properties of KCT add

Authors: Jungrae Noh Juhyun Yoo

Publish Date: 2013/01/06

Volume: 30, Issue: 3, Pages: 139-144

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Abstract

In this study Li002Na056 K046098Nb081Ta015Sb004O3 + x mol K54Cu13Ta10O29 ceramics were fabricated by conventional solidstate solution processes Then their dielectric and piezoelectric properties were investigated Sinterability of all samples was enhanced because K54Cu13Ta10O29 abbreviated as KCT acted as sintering aids As the result of XRD phase structure showed orthorhombic symmetry when KCT ≤ 02 mol Whereas the phase structure changed from orthorhombic symmetry to tetragonal symmetry when KCT ≥ 04 mol The results suggest that the orthorhombic and tetragonal phases coexist in the composition ceramics with 02 mol KCT 04 mol at room temperature The effects of the addition of KCT on the dielectric and piezoelectric properties were investigated As the result excellent properties of density=481g/cm3 electromechanical coupling factor kp=048 and piezoelectric constantd33=252pC/N were obtained in the composition ceramics with 04 molKCTPiezoelectric ceramics have been developed from BaTiO3based compositions to PbZrTiO3 based compositions Among them Lead zirconate titanate based abbreviated as PZT ceramics have been widely used in actuator sensors resonator transducer and energy harvesters due to their excellent piezoelectric and dielectric properties However these lead based ceramics can cause serious environmental pollution and damage human health due to generation of toxic PbO during the process of manufacturing Thus electrical waste and electronic equipment WEEE and restriction of hazardous substances RoHS have been enforced to new electronic products for the environmental production and human health Therefore leadfree piezoelectric ceramics such as BNTbased materials and NKN based materials have been studied during the past decadeAmong these N05 K05NbO3 abbreviated as NKN ceramics is a promising candidate for replacing leadfree ceramics due to their strong piezoelectricity and ferroelectricity Typically well sintered KNN ceramics have excellent physical properties such as a piezoelectric constant d 33 =80pC/N electromechanical coupling factor k p =36–40  mechanical quality factor Q m =130 and high curie temperature Tc~420 °C However the physical properties of the ceramics are still weak for application in piezoelectric devicesRecently special sintering processes such as Spark Plasma sintering SPS Hot pressing Hot forging and RTGG Reactive template grain growth have been utilized for manufacturing high performance ceramics 1 However the methods using these special sintering processes have high manufacturing costs Therefore new methods for manufacturing high performance ceramics have been introduced by using sintering aids such as CuO 2 ZnO Ta2O5 3 4 5 6 KNbO3 7 LiNbO3and K54Cu13Ta10O29 KCT 8 9 10 11 12 13 14 They can be added in the basic composition ceramics to form a solid solution Ta2O5 can be not only good sintering aids by the formation of K54Cu13Ta10O29 KCT 8 9 10 11 12 13 14 but also may act as the Ta5+ ion substituted at the Bsite of the ABO3 perovskite structure which make phase transition temperature orthorhombictetragonal phase transition TOT and tetragonalcubic phase transition TC decrease toward room temperature In addition potassium K of KCT acted as the compensating material for the volatilization of potassiumThe raw materials Na2CO3 995  K2CO3 995  Sb2O5 999  Nb2O5 999  CuO 999  Li2CO3 99  and Ta2O5 9995  for the given composition were weighted by mole ratio and the powders were ballmilled for 24 h After drying they were calcined at 900 °C and 950 °C for 6 h and 5 h respectively Thereafter KCT was added as sintering aids and then the specimens were ballmilled and dried again Polyvinyl alcohol PVA 5 wt aqueous solution was subsequently added to the dried powders The powders were molded under pressure of 2000 kg/cm2 burned out at 600 °C for 3 h and then sintered at 1100~1120 °C for 5 h The dimensions of the specimens were 172 Φ diameter× 1 mmthickness Poling was carried out at 100 °C in a silicon oil bath by applying a field of 3 kV/mm for 30 min In order to investigate the dielectric properties capacitance was measured at 1 kHz using an LCR meter ANDO AG4034 and the dielectric constant ε r was calculated Piezoelectric constants were obtained using a d 33 meter APC 8000 piezo d 33 tester For investigating the piezoelectric properties the resonant and antiresonant frequencies were measured by an Impedance Analyzer Agilent 4294A according to the IEEE standard and then k p and Q m were calculated 17

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