Mg—Ta based dielectric ceramic for multi-layer ceramic capacitor and low-temperature preparation method thereof

A magnesium-tantalum (Mg—Ta) based dielectric ceramic for multi-layer ceramic capacitor, comprising a ceramic material and a modifier;

• wherein a chemical formula of the ceramic material is MgTa2O6;
• a formula of the modifier is A2CO3—BO—C2O3—SiO2 with a mass ratio of 31:17:36:16, A2CO3 consists of 20 wt. % of Li2CO3 and 11 wt. % of K2CO3;
• BO consists of 2 wt. % BaO, 5 wt. % of MnO and 10 wt. % of CuO;
• and C2O3 consists of 30 wt. % of B2O3 and 6 wt. % of Al2O3;
• a formula of the Mg—Ta based dielectric ceramic is MgTa2O6+2 wt. % of the modifier, the Mg—Ta based dielectric ceramic is prepared by a solid-state method, a main crystal phase of the Mg—Ta based dielectric ceramic is MgTa2O6 phase with a Trirutile structure;
• under a sintering temperature of 1150 degrees Celsius (° C.), a dielectric constant of the Mg—Ta based dielectric ceramic is 26.87, a dielectric loss of the Mg—Ta based dielectric ceramic is 1.71×10−4, and a value of a quality factor Q×f of the Mg—Ta based dielectric ceramic is 44398 GHz;
• and a temperature coefficient τε of the dielectric constant is stable and meets M2G temperature characteristics of (−55° C.:
• τε=−118 parts per million (ppm)/° C.;
• 85° C.:
• τε=−110 ppm/° C.);
• the Mg—Ta based dielectric ceramic for multi-layer ceramic capacitor is prepared through the following steps:
• step 1, mixing raw powders of magnesium oxide (MgO) and Ta2O5 according to the chemical formula MgTa2O6 to obtain a mixed powder;
• step 2, putting the mixed powder prepared in step 1 into a ball milling tank, using zirconium balls and deionized water as a grinding medium and performing planet ball milling for 4-6 hours according to a mass ratio of the mixed powder:the zirconium balls:the deionized water of 1:4-5:2-4 to obtain a mixed slurry, drying the mixed slurry in an oven after the planet ball milling and then sieving with a 60-100 mesh sieve to obtain a sieved powder;
• and sintering the sieved powder in an atmosphere of 900-1000° C. for 3-5 hours to obtain MgTa2O6;
• step 3, mixing raw powders of Li2CO3, K2CO3, BaO, MnO, CuO, B2O3, Al2O3, and SiO2 according a mass ratio of Li2CO3:K2CO3:BaO:MnO:CuO:B2O3:Al2O3:SiO2 of 20:11:2:5:10:30:6:16 to obtain a second mixed powder;
• using the zirconium balls and alcohol as a grinding medium and performing planet ball milling for 6-8 hours according to a mass ratio of the second mixed powder:the zirconium balls:the alcohol of 1:4-5:4-6 to obtain a ball-milled material, sintering the ball-milled material at a temperature of 600-650° C. for 3-6 hours after drying the ball-milled material and then heating to a temperature of 1450-1550° C. for melting for 3-5 hours to obtain a melted material, pouring the melted material into the deionized water for cooling to obtain a cooled material, and grinding the cooled material to a uniform power as the modifier;
• step 4, mixing the modifier prepared in step 3 into MgTa2O6 prepared in step 2 according to the formula of the Mg—Ta based dielectric ceramic MgTa2O6+2 wt. % to obtain a third mixed power, performing planetary ball milling for 3-5 hours according to a mass ratio of the third mixed powder:the zirconium balls:the deionized water of 1:4-5:3-5 to obtain a second ball-milled material, and adding a polyvinyl alcohol solution, as a binder, into the second ball-milled material after drying the second ball-milled material to perform granulation to obtain a granular material;
• and
• step 5:
• performing press-molding on the granular material prepared in step 4, heating at a heating rate of 2-5° C./minutes (min) and discharging glue at 600-650° C. for 3-5 hours, and then heating at the same heating rate to a temperature of 1150° C. and keeping the temperature for 4-6 hours, thereby obtaining a modified MgTa2O6 dielectric ceramic material.