Two series of B-site deficient perovskites Ba_(5+m)Ti_(m)Nb_(4)O_(15+3m)(m=1,2,3)and Sr_(3+m)LaTi_(m)Nb_(3)O_(12+3m)(m=0,1,2)with the general formula A_(n)B_(n-1)O_(3n)(n=4-8;A=Ba,Sr,La;B=Nb,Ti)have been synthesized,and their structure and microwave dielectric properties have been investigated.The effects of n(number of octahedra layers within a perovskite blocks)on structure and properties are investigated.The values of dielectric constantε_(r)and temperature coe±cient of resonant frequencyτ_(f)gradually increase,but quality factors Q×f values significantly decreases as the values of n increase.
