MnO₂as an Effective Sintering Aid for Enhancing Piezoelectric Properties of (K,Na)NbO₃Ceramics

Further Enhancing Piezoelectric Properties by Adding MnO2 in AgSbO3‐Modified (Li,K,Na)(Nb,Ta)O3 Lead‐Free Piezoceramics

“…In addition, more rectangular P-E loops were observed in the Mn-modified samples, especially for the sample with x = 0.5. [22][23][24][25][30][31][32] Mn cation is considered to be incorporated into the B-site of the lattice in KNN single crystal, but cation deficiency in KNN-based ceramics is more complicated specially for the complex composition, the alkali evaporation, and the multivalence (Mn 2+ : 91 pm, Mn 3+ : 70 pm, and Mn 4+ : 54 pm) of Mn ions during the formation of solid solutions. 4(b).…”

“…,24 Here, it is conjectured that A-site is preferred by Mn cations (donor doping) in this KNN-based solution and some of the Mn cations enter the B sites (acceptor doping) when excessive MnO 2 is doped as elucidated in other literatures [22][23][24][25][30][31][32]. …”

“…10 With the purpose to make a balance between maintaining good piezoelectric property and enhancing thermal stability, the PPT effect though phase manipulation should be retained because it is accepted as an indispensable way for piezoelectric property enhancement in KNN-based ceramics. [1][2][3]5,7,18,19,[21][22][23][24][25] However, the enhancement merely dependent on PPT effect could lead to the high sensitivity to temperature fluctuation in KNN-based ceramics. The drawbacks might be partially counteracted by further enhancement of the piezoelectric property via some other mechanisms.…”

“…The drawbacks might be partially counteracted by further enhancement of the piezoelectric property via some other mechanisms. [27][28][29] Besides, MnO 2 is deemed as one of the most intriguing additives in KNN-based ceramics because both "softening" or "hardening" characteristics of MnO 2 are simultaneously observed, which conduce to the increases in piezoelectric constant d 33 , relative permittivity e r , planar electromechanical coupling factor k p , and mechanical quality factor Q m , as well as the decrease in loss tangent tan d. [22][23][24][25][30][31][32] It has been found that a gentle decrease in T O-T and piezoelectric property enhancement could be achieved by the addition of AgSbO 3 . 26 On the basis of the following literature results, incorporating MnO 2 into a compositionally optimized KNN-based ceramics with adjusted PPT should be studied as a solution.…”

“…It has been reported that MnO 2 addition could endow single crystals of KNN systems with a better piezoelectric response by modifying domain structure or lattice defects. [27][28][29] Besides, MnO 2 is deemed as one of the most intriguing additives in KNN-based ceramics because both "softening" or "hardening" characteristics of MnO 2 are simultaneously observed, which conduce to the increases in piezoelectric constant d 33 , relative permittivity e r , planar electromechanical coupling factor k p , and mechanical quality factor Q m , as well as the decrease in loss tangent tan d. [22][23][24][25][30][31][32] It has been found that a gentle decrease in T O-T and piezoelectric property enhancement could be achieved by the addition of AgSbO 3 . 33 As reported in previous work, 16,19 promising piezoelectric properties were achieved by the precise control of PPT point around room temperature in the AgSbO 3 -modified (Li, K, Na)(Nb,Ta)O 3 ceramics.…”