High-temperature BaTiO_(3) -based ceramic capacitors by entropy engineering design

High-performance BaTiO_(3)(BTO)-based dielectric ceramics have great potential for high-power energy storagedevices. However, its poor temperature reliability and stability due to its low Curie temperature impedes the development ofmost electronic applications. Herein, a series of BTO-based ceramics are designed and prepared on the basis of entropyengineering. Owing to the incorporation of Bi(Mg_(0.5)Ti_(0.5))O_(3), relaxation behavior and low dielectric loss at high temperatureshave been achieved. Moreover, the high-entropy strategy also promotes lattice distortion, grain refinement and excellentresistance, which together increase the breakdown field strength. These simultaneous effects result in outstanding energystorage performance, ultimately achieving stable energy density (U_(e)) of 5.76 J·cm^(−3) and efficiency ( η) of 89%. Mostimportantly, the outstanding temperature stability makes high-entropy BTO-based ceramics realize a significant energystorage density of 4.90 0.14 J·cm^(−3) with the efficiency above 89%, spanning a wide temperature range of 25–250 ℃, aswell as cycling reliability with negligible performance deterioration after 3 105 cycles at 300 kV∙cm^(−1) and 200 ℃. Thisresearch presents an effective method for designing temperature-stable and reliable dielectrics with comprehensive energystorage performance.

High piezoelectric properties and good temperature stabilities of CuO-modified Ba(Ti_(0.96)Sn_(x)Zr_(0.04-x))O_(3) ceramics

In order to obtain both high piezoelectric property and good temperature stability in BaTiO_(3)-based ceramics in the common usage temperature range,Sn4þand Zr4þare co-doped into BaTiO3 ceramics according to the formula of Ba(Ti_(0.96)Sn_(x)Zr_(0.04-x))O_(3)(BTSZ)(x=0.01-0.4)with 1 mol%CuO being added as sintering-aid in this study.The CuO-modified BTSZ ceramics show both high piezoelectric properties and good temperature stability.Particularly,the CuO-modified Ba(Ti_(0.96)Sn_(x)Zr_(0.04-x))O_(3)ceramic displays the high piezoelectric properties of d_(33)=350 pC/N,k_(p)=49.5%at room-temperature and a weak temperature dependence of kp in the temperature range of
15C and 60C.Moreover,the CuO-modified Ba(Ti_(0.96)Sn_(x)Zr_(0.04-x))O_(3)ceramic shows stable thermal aging behavior with the d33 being almost unchanged until the aging temperature of 100C,which is even higher than its Curie temperature.The high piezoelectric properties of CuO-modified Ba(Ti_(0.96)Sn_(x)Zr_(0.04-x))O_(3)ceramic were ascribed to the dense microstructure with small and uniform grain size distribution.The stable thermal aging behavior can be explained by the aging effect based on the defect dipolar model.

HIGH PIEZOELECTRIC PERFORMANCE AND RELEVANT PHYSICAL MECHANISM OF CuO-MODIFIED Ba(Ti_(0.96)Sn_(0.04))O_(3)CERAMICS

Ba(Ti_(0.96)Sn_(0.04))O_(3)and CuO-modified Ba(Ti_(0.96)Sn_(0.04))O_(3)ceramics were prepared by the solid state reaction technique.Their piezoelectric properties were investigated and compared with those of the recently obtained high-d_(33)BaTiO_(3)ceramic.It has been found that simply substituting Ti4t with Sn4t worsens severely the piezoelectric properties whereas a combined usage of CuO additive greatly improves the overall piezoelectric performance.CuO-modified BaeTi_(0.96)Sn_(0.04)TO_(3)ceramic shows excellent piezoelectric properties of d_(33)=390 pC=N;kp=0.49 and k33=0.67 at room temperature.Furthermore,it possesses weak temperature dependences of electromechanical coe±cients between
20 and 55 and a good thermal aging stability down to a low experimental temperature limit of
50℃and up to 90.Detailed analysis suggests that its high piezoelectric performance should be largely ascribed to the ideal microstructure of high relative density and small grains and the corresponding domain configurations.