| [1] | AKSEL E, JONES J L. Advances in lead-free piezoelectric materials for sensors and actuators. Sensors, 2010,  10(3): 1935. DOI    
																																																	PMID
 | 
																													
																						| [2] | RODEL J, WEBBER K G, DITTMER R, et al. Transferring lead-free piezoelectric ceramics into application. J. Eur. Ceram. Soc., 2015,  35(6):1659. DOI    
																																					URL
 | 
																													
																						| [3] | DAMJANOVIC D.  Ferroelectric, dielectric and piezoelectric properties of ferroelectric thin films and ceramics. Rep. Prog. Physics, 1998,  61(9):1267. DOI    
																																					URL
 | 
																													
																						| [4] | RODEL J, LI F. Lead-free piezoceramics: status and perspectives. MRS Bull., 2018,  43(8):576. DOI    
																																					URL
 | 
																													
																						| [5] | PISARENKO G, KOVALEV S P, CHUSHKO V M. Fracture toughness of piezoelectric ceramics. Strength Mater., 1980,  12(12):1492. DOI    
																																					URL
 | 
																													
																						| [6] | RODIG T, SCHONECKER A, GERLACH G. A survey on piezoelectric ceramics for generator applications. J. Am. Ceram. Soc., 2010,  93(4):901. DOI    
																																					URL
 | 
																													
																						| [7] | GALLEGO-JUAREZ J A. Piezoelectric ceramics and ultrasonic transducers. J. Phys. E Sci. Instrum., 1989,  22(22):804. DOI    
																																					URL
 | 
																													
																						| [8] | PFERNER R A, THURN G, ALDINGER F. Mechanical properties of PZT ceramics with tailored microstructure. Mater. Chem. Phys., 1999,  61(1):24. DOI    
																																					URL
 | 
																													
																						| [9] | LI F X, FANG D N, SOH A K. Theoretical saturated domain- orientation states in ferroelectric ceramics. Scr. Mater., 2006,  54(7):1241. DOI    
																																					URL
 | 
																													
																						| [10] | CALDERON-MORENO J M, POPA M. Fracture Toughness Anisotropy by Indentation and SEVNB on Tetragonal PZT Polycrystals. 12th Meeting of the International Conference on the Strength of Materials (ICSMA 12), 2001, 319: 692. | 
																													
																						| [11] | LI Y W, LI F X. Large anisotropy of fracture toughness in mechanically poled/depoled ferroelectric ceramics. Scr. Mater., 2010,  62(5):313. DOI    
																																					URL
 | 
																													
																						| [12] | CALDERON-MORENO J M, GUIU F, MEREDITH M, et al. Fracture toughness anisotropy of PZT. Mater. Sci. Eng. A, 1997,  234-236(1):1062. DOI    
																																					URL
 | 
																													
																						| [13] | MEHTA K, VIRKAR A V. Fracture mechanisms in ferroelectric- ferroelastic lead zirconate titanate (Zr: Ti=0.54:0.46) ceramics. J. Am. Ceram. Soc., 1990,  73(3):567. DOI    
																																					URL
 | 
																													
																						| [14] | LUCATO SLDE; LUPASCU DC; RODEL J. Effect of poling direction on R-curve behavior in lead zirconate titanate. J. Am. Ceram. Soc., 2000,  83(2):424. DOI    
																																					URL
 | 
																													
																						| [15] | FETT T, GLAZOUNOV A, HOFFMANN M J, et al.  On the interpretation of different R-curves for soft PZT. Eng. Fract. Mech., 2001,  68(10):1207. DOI    
																																					URL
 | 
																													
																						| [16] | SEO Y H, VOGLER M, ISAIA D, et al. Temperature-dependent R-curve behavior of Pb(Zr1-xTix)O3. Acta Mater., 2013,  61(17):6418. DOI    
																																					URL
 | 
																													
																						| [17] | SCHNEIDER G A. Influence of electric field and mechanical stresses on the fracture of ferroelectrics. Annu. Rev. Mater. Res., 2007, 37: 491. | 
																													
																						| [18] | LI Y W, LIU Y, OCHSNER P E, et al. Temperature dependent fracture toughness of KNN-based lead-free piezoelectric ceramics. Acta Mater., 2019, 174: 369. | 
																													
																						| [19] | KUNA M. Fracture mechanics of piezoelectric materials-where are we right now? Eng. Fract. Mech., 2010,  77(2):309. DOI    
																																					URL
 | 
																													
																						| [20] | WEBBER K G, VOGLER M, KHANSUR N H, et al. Review of the mechanical and fracture behavior of perovskite lead-free ferroelectrics for actuator applications. Smart Mater. Struct., 2017,  26(6):063001. DOI    
																																					URL
 | 
																													
																						| [21] | KIM S B, KIM D Y, KIM J J, et al.  Effect of grain size and poling on the fracture mode of lead zirconate titanate ceramics. J. Am. Ceram. Soc., 1990,  73(1):161. DOI    
																																					URL
 | 
																													
																						| [22] | GUILLON O, THIEBAUD F, PERREUX D, et al.  New considerations about the fracture mode of PZT ceramics. J. Am. Eur. Soc., 2005, 25: 2421. | 
																													
																						| [23] | KUBLER J. Fracture toughness of ceramics using the SEVNB method a joint VAMSA/ESIS round robin. Fract. Mech. Ceram., 2002, 13: 437. | 
																													
																						| [24] | SALEM J A. Fracture toughness of advanced ceramics at room temperature. J. Res. Natl. Inst. Stand. Technol., 1992,  97(5):579. DOI    
																																																	PMID
 | 
																													
																						| [25] | VOGLER M, FETT T, RODEL J. Crack-tip toughness of lead-free (1-x)(Na1/2Bi1/2)TiO3-xBaTiO3 piezoceramics. J. Am. Ceram. Soc., 2018,  101(12):5304. DOI    
																																					URL
 | 
																													
																						| [26] | LI F X, SOH A K. An optimization-based computational model for domain evolution in polycrystalline ferroelastics. Acta Mater., 2010,  58(6): 2207. DOI    
																																					URL
 | 
																													
																						| [27] | BERMEJO R, DELUCA M. Mechanical characterization of PZT ceramics for multilayer piezoelectric actuators. J. Ceram. Sci. Technol., 2012,  3(4):159. | 
																													
																						| [28] | BERMEJO R, GRUNBICHLER H, KREITH J, et al.  Fracture resistance of a doped PZT ceramic for multilayer piezoelectric actuators: Effect of mechanical load and temperature. J. Eur. Ceram. Soc., 2010,  30(3):705. DOI    
																																					URL
 | 
																													
																						| [29] | JELITTO H, KEBLER H, SCHNEIDER G A, et al. Fracture behavior of poled piezoelectric PZT under mechanical and electrical loads. J. Eur. Ceram. Soc., 2005,  25(5):749. DOI    
																																					URL
 | 
																													
																						| [30] | DENKHAUS S M, VOGLER M, NOVK N, et al.  Short crack fracture toughness in (1-x)(Na1/2Bi1/2)TiO3-xBaTiO3 relaxor ferroelectrics. J. Am. Ceram. Soc., 2017,  100(10):4760. DOI    
																																					URL
 |