Ca^(2+)掺杂堇青石陶瓷的微波介电及力学性能

Microwave Dielectric and Mechanical Property of Cordierite Ceramics by Ca^(2+) Doping

采用溶胶凝胶法制备得到系列Ca^(2+)掺杂堇青石((Mg_(1-x)Ca_(x))_(2)Al_(4)Si_(5)O_(18))陶瓷粉体,研究Ca^(2+)取代Mg^(2+)对堇青石陶瓷的烧结特性、结构组成、微波介电性能及力学性能的影响。结果表明,Ca^(2+)的引入会提升粉体的烧结活性,能够有效促进样品的致密化烧结。当x≤0.1时,Ca^(2+)会全部进入堇青石结构中形成固溶体,为单一α-堇青石相;当x>0.1时,检测到有钙长石相的存在。Ca^(2+)取代Mg^(2+)能有效降低堇青石陶瓷的介电常数,提高品质因数、谐振频率温度系数及断裂韧性。当x=0.1时,(Mg_(1-x)Ca_(x))_(2)Al_(4)Si_(5)O_(18)陶瓷获得最优性能,介电常数为4.61,品质因数为9949 GHz,谐振频率温度系数为-26×10^(-6)℃^(-1),断裂韧性为4.76 MPa·m^(1/2)。

A series of Ca^(2+)-doped cordierite((Mg_(1-x)Ca_(x))_(2)Al_(4)Si_(5)O_(18))ceramic powders were prepared by a solgel method.The effect of the substitution of Ca^(2+) for Mg^(2+) of cordierite ceramics on the sintering properties,structural characteristics,microwave dielectric properties and fracture toughness was investigated.The results show that the introduction of Ca^(2+) can improve the sintering activity of the powder,thus improving the density of the sample and the sintering densification.The singleα-cordierite phase is obtained in the range of 0<x≤0.1 because Ca^(2+) is doped into the cordierite structure to form the solid solution.When the x value is larger than 0.1,an anorthite phase appears.The dielectric constant of cordierite ceramic decreases,and the quality factor,the temperature coefficient of frequency and fracture toughness improve when Mg^(2+) substitutes for Ca^(2+).The optimum performance of(Mg_(1-x)Ca_(x))_(2)Al_(4)Si_(5)O_(18) ceramic is obtained when the x value is 0.1,i.e.,the dielectric constant of 4.61,the quality factor of 9949GHz and the temperature coefficient of frequency of-26×10^(-6)/℃,and the fracture toughness of 4.76MPa·m^(1/2).