{'fraction_non_alphanumeric': 0.032428355957767725, 'fraction_numerical': 0.05128205128205128, 'mean_word_length': 4.670940170940171, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Lithium-induced dielectric relaxations in potassium tantalate ceramics

This work reports the effect of lithium doping on the dielectric and polar properties of potassium tantalate. Experimental data were obtained in K1−xLixTaO3 ceramics with x = 0, 0.02, 0.05 and 0.10 by measuring both the dielectric permittivity from 102 to 108 Hz, and polarization under an ac electric field driven at 2.5 Hz, for temperatures from 10 to 300 K. The dielectric permittivity exhibits all the relaxations reported for K1−xLixTaO3 single crystals. Two dielectric relaxations observed at 40–125 K are ascribed to the individual hopping by 90° and 180° of dipoles created by the off-centre Li ions. Another relaxation observed at 100–200 K is related to 180°-flips of Li pairs for x = 0.02 and of polar clusters of interacting Li ions for x = 0.05 and 0.10. In addition to that, an additional relaxation not reported before is presented at 135–235 K for x = 0.10 and attributed to 90°-reorientation of Li polar clusters. Both the change from an Arrhenius to a Vogel–Fulcher dependence with increasing lithium content, and the emergence of slim P (E) hysteresis loops around the relaxation temperatures show that the relaxation dynamics in K1−xLixTaO3 can be understood if a crossover from a dipolar glass to a relaxor-like behaviour is assumed.