The Research On The Doping Modification And Dielectric Properties Of (K_0.5Na_0.5)NbO₃-based Dielectric Ceramics

With the development of high-tech industries of control,communication,electronics and so on,electronic devices are required to have good thermal stability.So it has great significance to study electronic ceramics with good dielectric properties.As one kind of lead-free ceramics,(K_0.5Na_0.5)NbO₃ based systems exhibited large relative permittivity,high Curie temperature?420^oC?and environmental friendly performance.The(K_0.5Na_0.5)NbO₃ can operate at higher temperatures,which is an excellent candidate to displace PZT ceramics.However,it is very difficult to acquire a dense(K_0.5Na_0.5)NbO₃ ceramics using the traditional solid sintering method because of the volatility of alkaline elements at high temperatures.The improvement of the pure(K_0.5Na_0.5)NbO₃ properties has far-reaching significance.Donor-doping was an effective approach to improve the dielectric properties.?1-x?(K_0.5Na_0.5)NbO₃-xBi(Mg_0.5Zr_0.5)O₃??1-x?(K_0.5Na_0.5)NbO₃-xBi(Li_1/3Zr_2/3)O₃??1-x?(K_0.5Na_0.5)NbO₃-xBi(Li_0.5Nb_0.5)O₃??1-x?(K_0.5Na_0.5)NbO₃-xBi(Cu_0.75W_0.25)O₃??1-x?(K_0.5Na_0.5)NbO₃-xBi(Mg_0.75W_0.25)O₃ ceramics were fabricated by traditional solid-state reaction sintering method,the dielectric properties were also studied systematically in this paper.The test results indicated that all ceramics possessed a pure perovskite structure and no secondary phase was detected.The grain size was gradually decreased,indicating that the additive could inhibit the grain growth of ceramics.The main contents were as follows:?1?The 0.9925(K_0.5Na_0.5)NbO₃-0.0075Bi(Mg_0.5Zr_0.5)O₃ ceramics showed optimized high relative permittivity??²024?,low dielectric loss?tan??27?3.8%?and good thermal stability(??/?_143°C?±10%)over a wide temperature range of143^oC³37^oC.?2?The 0.995(K_0.5Na_0.5)NbO₃-0.005Bi(Li_1/3Zr_2/3)O₃ ceramics exhibited high relative permittivity??²160?,low dielectric loss?tan??27?2.5%?and good thermal stability(??/?_154°C?±10%)in the temperature range of 154^oC³70^oC.?3?The 0.99(K_0.5Na_0.5)NbO₃-0.01Bi(Li_0.5Nb_0.5)O₃ ceramics exhibited low dielectric loss?tan??27?2.4%?and good thermal stability(??/?_150°C?±10%)in the temperature range of 150^oC³64^oC.?4?The 0.99(K_0.5Na_0.5)NbO₃-0.01Bi(Cu_0.75W_0.25)O₃ ceramics exhibited low dielectric loss?tan??27?2.8%?and good thermal stability(??/?_150°C?±15%)in the temperature range of 150³67^oC.Especially,the thermal stability??/?_150°C?±15%has a broader temperature range from 150^oC to 500^oC as x=0.025.?5?The 0.995(K_0.5Na_0.5)NbO₃-0.005Bi(Mg_0.75W_0.25)O₃ ceramics exhibited low dielectric loss?tan??27?2.9%?and good thermal stability(??/?_168°C?±15%)in the temperature range of 168³69^oC.Especially,the(K_0.5Na_0.5)NbO₃-Bi(Mg_0.75W_0.25)O₃ceramics also showed optimized piezoelectric constant(d₃₃=122pC/N)and remnant polarization?P_r=32.57?C/cm²?.These results indicated that the piezoelectric and dielectric properties of the(K_0.5Na_0.5)NbO₃-based doped ceramics were better the pure(K_0.5Na_0.5)NbO₃ ceramics.