摘 要

作为微波滤波器和微波谐振器的关键性材料，在微波通信技术中微波介质陶瓷有着广泛的用途。钙钛矿结构的CaTiO₃具有较高的ε_r(170)和Q×f值(3600GHz)，但其τ_f为较大正值( 800ppm/℃)，因而无法实际运用。Li_1/2Nd_1/2TiO₃具有较大的负τ_f值，两者可以进行温度补偿而获得温度性能良好的高介陶瓷。本文采用固相法制备了CaTiO₃-Li_1/2Nd_1/2TiO₃(CLNT)，采用Sr² 离子对CLNT陶瓷进行A位改性，再加入BiO₃、Bi₂O₃-B₂O₃、Bi₂O₃-2B₂O₃，探究添加剂在陶瓷的微波介电性能和烧结特性上的影响。主要研究内容如下：

1. 采用固相合成法制备0.2CaTiO₃-0.8Li_1/2Nd_1/2TiO₃(CLNT)陶瓷，其介电性能为：ε_r=120.9，Q×f=1160GHz，τ_f = 5.4ppm/℃。

2.采用Sr² 离子对CLNT陶瓷进行A位改，0.2Ca_15/16Sr_1/16TiO₃-0.8Li_1/2Nd_1/2TiO₃(CSLNT)陶瓷获得了更优的介电性能：ε_r=132.3，Q×f =2310GHz，τ_f = 52.2ppm/℃

3.为了进一步降低烧结温度，同时调节频率温度系数，选择BiO₃、Bi₂O₃-B₂O₃、2Bi₂O₃-B₂O₃作为三种添加剂，研究其对0.2Ca_15/16Sr_1/16TiO₃-0.8Li_1/2Nd_1/2TiO₃陶瓷烧结行为和介电性能的影响。

（1）当添加剂为Bi₂O₃时，伴随着Bi₂O₃的加入，介电常数开始减小，同时品质因数先增大后减小，频率温度系数向负的方向移动。当添加剂的添加量为5wt%时，烧结温度为1300℃时，获得了介电性能为：ε_r=130.7，Q×f=2370GHz，τ_f =7.6ppm/℃ 。

（2）随着Bi₂O₃-B₂O₃的加入，介电常数减小。加入适量的Bi₂O₃-B₂O₃，可以有效降低烧结温度，同时调节频率温度系数至近零。当添加加量为5wt%时，烧结温度为1200℃时，获得了介电性能为：ε_r=130.7，Q×f=2210GHz，τ_f =2.2ppm/℃ 。

（3）随着Bi₂O₃-2B₂O₃的加入，介电常数与品质因数刚开始维持稳定。当添加量超过5wt%时，介电常数和品质因数呈现明显的退化。加入适量的Bi₂O₃-2B₂O₃可以有效降低烧结温度和调节频率温度系数，当加入5wt% Bi₂O₃-2B₂O₃，烧结温度在1150℃时，得到的陶瓷微波介电性能：ε_r=127.4，Q×f=2260GHz，τ_f =-4.4ppm/℃。

关键词：CaTiO₃；钙钛矿结构；微波介电性能；烧结助剂

Abstract

Microwave dielectric ceramics are the key materials for microwave resonators and microwave filters, and have a wide range of applications in microwave communication technology. Perovskite structure CaTiO₃ have high ε_r(170) and Q×f(3600GHz)，but the τ_f for large positive( 800ppm/℃), and thus cannot be applied .Li_1/2Nd_1/2TiO₃ is a large negative value τ_f, both of which can be compensated by temperature to obtain a good temperature performance of high dielectric ceramics.The solid phase method to prepare CaTiO₃-Li_1/2Nd_1/2TiO₃(CLNT), a modification, add BiO₃、Bi₂O₃-B₂O₃、Bi₂O₃-2B₂O₃explore effect of additive on the ceramic sintering behavior and microwave dielectric properties of clnt ceramic with Sr² ions. The main research contents are as follows:

1. Solid-phase synthesis method was adopted to prepare the 0.2CaTiO₃-0.8Li_1/2Nd_1/2TiO₃ (CLNT) ceramic and its dielectric properties: ε_r=120.9，Q×f=1160GHz，τ_f = 5.4ppm/℃.

2. The Sr² ion on CLNT ceramic were a modified, ceramic obtained better dielectric electrical properties: ε_r=132.3，Q×f =2310GHz，τ_f = 52.2ppm/℃.

3.The effect of different sintering additives Bi₂O₃, Bi₂O₃-B₂O₃ and Bi₂O₃-2B₂O₃ on the sintering characteristics and microwave dielectric properties of the sintering aids were as follows:

(1) When the additive Bi₂O₃, with the addition of Bi₂O₃, the dielectric constant decreases, the quality factor increases first and then decreases, and the frequency temperature coefficient moves toward the negative direction. When the adding amount of 5wt%, the sintering temperature for 1300℃ , dielectric electrical properties: ε_r=130.7，Q×f=2370GHz，τ_f =7.6ppm/℃.

(2)With the addition of Bi₂O₃-B₂O₃, the dielectric constant decreases. By adding proper amount of Bi₂O₃-B₂O₃, the sintering temperature can be effectively reduced, and the frequency temperature coefficient of the sintering temperature can be adjusted to near zero. When the adding of the added amount of 5wt%, the sintering temperature to 1200℃, dielectric properties: ：ε_r=130.7，Q×f=2210GHz，τ_f =2.2ppm/℃.

(3) With the addition of Bi₂O₃-2B₂O₃, the dielectric constant and the quality factor are just beginning to maintain stability. When the added amount exceeds 5wt%, the dielectric constant and the quality factor show obvious degradation. Adding the right amount of Bi₂O₃-2B₂O₃ can effectively lower the sintering temperature and adjust the temperature coefficient of frequency. When the addition of 5wt% Bi₂O₃-2B₂O₃, get the microwave dielectric electrical properties: ε_r=127.4，Q×f=2260GHz，τ_f =-4.4ppm/℃。

Key Words: CaTiO₃；Perovskite structure；Microwave dielectric properties；Sintering additives

目 录