Minimization of pyroelectric effects in relaxor-PbTiO₃ crystals for piezoelectric sensors

To minimize pyroelectric effects while keeping high piezoelectric effects in relaxor-PbTiO₃ single crystals, the crystallographic orientation dependence of the pyroelectric and piezoelectric coefficients were investigated for binary (1 - x)Pb(Mg_1/3Nb_2/3)O₃-xPbTiO ₃ (PMN-PT), ternary (1 - x - y)Pb(In_1/2Nb _1/2)O₃-yPb(Mg_1/3Nb_2/3)O ₃-xPbTiO₃ (PIN-PMN-PT) and Mn-doped PIN-PMN-PT single crystals with the "4R" multidomain state. The secondary pyroelectric coefficients were calculated from the thermodynamic inter-relationship between the piezoelectric, elastic, and thermal expansion coefficients, being on the order of (1.16-1.23) × 10^-4 C m^-2 K^-1 for binary crystals and (0.97-2.03) × 10^-4 C m^-2 K ^-1 for ternary ones. The primary pyroelectric coefficients were -(6.73-6.84) × 10^-4 C m^-2 K^-1 and -(5.44-6.43) × 10^-4 C m^-2 K^-1 for binary and ternary crystals, respectively. The pyroelectric coefficients could be reduced by matrix rotation, but at the cost of decreasing longitudinal piezoelectric coefficients d₃₃. Of particular interest is that the maximum piezoelectric coefficients d24â̂ - at θ = ±55^o and d34â̂ - at θ = ±35 ^o by a counterclockwise rotation of θ about the X axis (θ is the rotation angle about the coordinate axes), or d15â̂ - at θ = ±55^o, and d35â̂ - at θ = ±35^o by a counterclockwise rotation the Y axis, were found on the order of 3000 pC N^-1. The corresponding pyroelectric coefficients could be reduced by ∼20%. The reduced pyroelectric coefficients that can contribute to decrease undesirable output signals, together with the high piezoelectric coefficients, enable relaxor-PT crystals as favorable candidates for high-sensitivity piezoelectric sensors.