Quantum limit of ferroelectric phase transitions in KTa1-xNbxO3

Dielectric and elastic constants of KTa1-xNbxO3 are presented as a function of x and of the temperature. For x=8×10-3, the system exhibits the characteristics of a ferroelectric at the displacive limit (i.e., a "quantum ferroelectric") as evidenced by three critical indices and the temperature independence of all responses near T=0. © 1977 The American Physical Society.