The electrocaloric effect of ferroelectric materials,which occurs significantly near the first-order paraelectric/ferroelectric transition Curie temperature,has tremendous prospect in solid-state cooling devices.In the present work,thermodynamics analysis and phase field simulations were conducted to demonstrate the uniaxial mechanical compressioninduced two types of pseudo-first-order phase transition,which could occur at a temperature below the Curie temperature.Thus,in one material there may coexist ultrahigh positive and negative electrocaloric effects,which are associated with the two pseudo-first-order phase transitions and tunable by the magnitude of the uniaxial compression.The uniaxial mechanical compressioninduced pseudo-first-order phase transition and the coexistence of positive and negative electrocaloric effects establish a novel technology to design and manufacture next generation of solid-state cooling devices.