Rapid heating thermal shock study of ultra high temperature ceramics using an in situ testing method

In this paper,the rapid cooling thermal shock behaviors of ZrB_(2)-SiC ceramics were measured using traditional water quenching method,and the rapid heating thermal shock behaviors of ZrB_(2)-SiC ceramics were investigated using a novel in situ testing method.The measured critical thermal shock temperature difference for rapid cooling thermal shock was 373.6℃;however,the critical thermal shock temperature difference for rapid heating thermal shock of ZrB_(2)-SiC ceramics was measured to be as high as 1497.2℃.The thermal stress distribution states after rapid cooling thermal shock and rapid heating thermal shock testing were analyzed using finite element analysis(FEA)method.The FEA results showed that there is a tensile stress existed on the surface for rapid cooling thermal shock,whereas there is a compressive stress existed on the surface for rapid heating thermal shock.The difference of thermal stress distribution resulted in the difference of the critical temperature difference for rapid cooling thermal shock and rapid heating thermal shock.

Ceramic synthesis of 0.08BiGaO_3–0.90BaTiO_3–0.02LiNbO_3 under high pressure and high temperature

In this paper, the preparation of 0.08BiGaO3–0.90BaTiO3–0.02LiNbO3 is investigated at pressure 3.8 GPa and temperature 1100–1200？C. Experimental results indicate that not only is the sintered rate more effective, but also the sintered temperature is lower under high pressure and high temperature than those of under normal pressure. It is thought that the adscititious pressure plays the key role in this process, which is discussed in detail. The composition and the structure of the as-prepared samples are recorded by XRD patterns. The result shows that the phases of Ba TiO3, BaBiO（2.77）, and Ba2Bi4Ti5O（18） with piezoelectric ceramic performance generate in the sintered samples. Furthermore, the surface morphology characteristics of the typical samples are also investigated using a scanning electron microscope. It indicates that the grain size and surface structure of the samples are closely related to the sintering temperature and sintering time. It is hoped that this study can provide a new train of thought for the preparation of lead-free piezoelectric ceramics with excellent performance.

Review on high temperature piezoelectric ceramics and actuators based on BiScO_(3)–PbTiO_(3) solid solutions

In recent years,industries in the fields of petrochemical,automotive,and aerospace have expressed their interest in utilizing piezoelectric actuators for high-temperature(HT)operations at the temperature above 150℃.HT piezoelectric ceramics(1x)BiScO_(3-x)PbTiO_(3)(BS-PT)are considered as one of the most competitive piezoelectric actuation materials used in the harsh environment because of its high Curie temperature(T_(C)=450℃)as well as high piezoelectric coefficient(d_(33)=460 pC/N)in the MPB composition.This paper summarized the recent progress in HT piezoelectric ceramics and actuators based on BS-PT solid solutions.The properties of BS-PT piezoelectric ceramics and actuators,including driving mechanisms,actuation performances and their applications in HT environment were also discussed.

Measurement of wireless pressure sensors fabricated in high temperature co-fired ceramic MEMS technology

High temperature co-fired ceramics(HTCCs) have wide applications with stable mechanical properties,but they have not yet been used to fabricate sensors.By introducing the wireless telemetric sensor system and ceramic structure embedding a pressure-deformable cavity,the designed sensors made from HTCC materials(zirconia and 96% alumina) are fabricated,and their capacities for the pressure measurement are tested using a wireless interrogation method.Using the fabricated sensor,a study is conducted to measure the atmospheric pressure in a sealed vessel.The experimental sensitivity of the device is 2 Hz/Pa of zirconia and 1.08 Hz/Pa of alumina below 0.5 MPa with a readout distance of 2.5 cm.The described sensor technology can be applied for monitoring of atmospheric pressure to evaluate important component parameters in harsh environments.

Effect of temperature on phase transition behavior of antiferroelectric (Pb_(0.97)La_(0.02) )(Zr_(0.75)Sn_(0.25-x)Ti_x)O_3 ceramics

Pb0：97La0：02（Zr0：75Sn0：25x Ti x/O3（x D0.10, 0.105, 0.11）（PLZST） antiferroelectric ceramics with highly preferred-（110） orientation were successfully fabricated via the conventional solid-state reaction method.The antiferroelectric nature of PLZST ceramics induced by electric field was demonstrated by the dielectric constant-temperature（D-T） and the polarization-electric field（P-E） measurement. Typical phase transition from ferroelectric（FE） to antiferroelectric（AFE）, and then to paraelectric（PE） is obtained. The results indicate that the phase transition behavior is suppressed with increasing of x, and T c is remarkably shifted to higher temperature of168 ℃, 170 ℃ and 174 ℃, respectively. Besides, high phase transition current（110 6A, 810 7A and 610 7A, respectively） is obtained with temperature induced. Consequently, the excellent electric properties and the restraint between temperature and electric field would provide basis on the application of PLZST antiferroelectric ceramics in microelectronic integrated systems and sophisticated weapons systems.