科研之友
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摘要
The crystal structure and microwave dielectric properties of Ca[(Li1/3Nb2/3)(0.95)Zr-0.15]-O3+delta ceramic (CLNZ) are tuned by A-site substitution of Sr2+ and Ba2+ ions in the present paper. The tuning effect on the crystal structure is investigated by the X-ray diffraction (XRD) pattern and it illustrates that single phase of orthorhombic perovskite structure is formed, however, minor amount of BaNb2O6-type second phase is also detected in (Ca1-xBax)[(Li1/3Nb2/3)(0.95)Zr-0.15]O3+delta ceramics (CBLNZ) in the range of x >= 0.025, while pure perovskite phase is obtained in (Ca1-xSrx)[(Li1/3Nb2/3)(0.95)Zr-0.15]O3+delta ceramics (CSLNZ) in the whole investigation range of 0 <= x <= 0.2. With the increase of x value, the unit cell volumes of both CBLNZ and CSLNZ perovskites gradually expand, which results in the degradation of the vibration bond strength between the B-site ions and oxygen in the perovskites. The microscopic structure related thermal parameters in CSLNZ and CBLNZ perovskites are analyzed in terms of Clausius-Mossotti equation to reveal the original contributors in the temperature coefficients. The results show that both Sr2+ and Ba2+ substitution can effectively improve the permittivity and Qf value, especially, improve the temperature coefficient of CLNZ ceramic in a certain range.
