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We have synthesised ceramic specimens of the tetragonal tungsten bronzeK3Li2Ta5O15 (KLT) and characterized its phase transition via X-ray, dielectricpermittivity, ultrasonic spectroscopy and heat capacity measurements. The spacegroup of KLT is reported as both P4/mbm or Cmmm with the orthorhombicdistortion occurring when there are higher partial pressures of volatile K andLi used within the closed crucibles for the solid state synthesis. The datashow strong relaxor behaviour, with the temperature at which the two dielectricrelative permittivity peaks decreasing with 104 K $\geqslant$ Tm1 $\geqslant$69 K and 69 K $\geqslant$ Tm2 $\geqslant$ 46 K as probe frequency f is reducedfrom 1 MHz to 316 Hz. The data satisfy a Vogel-Fulcher model with anextrapolated freezing temperature for {\epsilon}' and {\epsilon}" of Tf1 = +15.8 and - 11.8 K and Tf2 = - 5.0 and - 15.0 K for f $\rightarrow$ 0 (tendingto dc). Therefore by tuning frequency, the transition could be shifted toabsolute zero suggesting KLT has a relaxor-type quantum critical point. Inaddition, we have reanalysed the conflicting literature for Pb2Nb2O7 pyrochlorewhich suggests that this is also a relaxor-type quantum critical point as thefreezing temperature from Vogel-Fulcher fitting is below absolute zero. Sincethe transition temperature evidenced in the dielectric data at ca. 100 kHzshifts below zero Kelvin for very low frequencies, heat capacity data collectedin the zero-frequency (dc) limit, should not indicate a transition. Both ofthese materials show promise as possible new relaxor-type quantum criticalpoints within non-perovskite based structures as multiple compounds arereported with low-temperature transitions.

Quantum Critical Points in Ferroelectric Relaxors: Stuffed Tungsten Bronze K3Li2Ta5O15 and Lead Pyrochlore (Pb2Nb2O7)